EP1654463B1

EP1654463B1 - Vacuum pump

Info

Publication number: EP1654463B1
Application number: EP03817522A
Authority: EP
Inventors: Sergio Bisetti
Original assignee: Progetti Srl AB
Current assignee: Progetti Srl AB
Priority date: 2003-07-18
Filing date: 2003-07-18
Publication date: 2007-09-05
Anticipated expiration: 2023-07-18
Also published as: ATE372465T1; DE60316199D1; EP1654463A1; AU2003253259A1; WO2005008074A1; DE60316199T2

Abstract

There is described a vacuum pump (1) having an outer casing (3) having at least one opening (5) connected to an environment in which a vacuum is to be formed; and a rotor (7) supplied with an operating liquid, and mounted to rotate about an axis (A) inside the casing (3) to produce, by movement of the operating liquid, a vacuum in the environment connected to the opening (5); the rotor (7) having generating means (50) for generating a screw-shaped stream of operating liquid to draw gaseous fluid by suction though the opening (5).

Description

TECHNICAL FIELD

The present invention relates to a vacuum pump, i.e. a pump for producing a vacuum or predetermined low pressure in an environment connected to it.

BACKGROUND ART

Vacuum pumps are known which operate on the principle of moving an operating liquid, normally water, along a curved path to draw a gaseous fluid, air or gas, by suction and centrifugal force from an environment communicating with the liquid-moving chamber.
More specifically, liquid-ring vacuum pumps are known, which substantially comprise a cylindrical casing or outer body having one or more inlet openings connected to a first environment, and one or more outlet openings connected to a second environment; and a rotor mounted to rotate inside the casing about an axis eccentric with respect to the casing axis, and having a number of contoured, substantially radial blades. In actual use, the casing is filled partly with operating liquid, and rotation of the rotor produces a ring of moving liquid. Because the rotor is eccentric with respect to the casing, along one angular section of the rotor's travel, the operating liquid is spun on to the casing wall, thus drawing up the gaseous fluid from the first environment, and, along another angular section of the rotor's travel, the operating liquid is moved towards the centre of the casing to expel the aspirated gaseous fluid through the outlet openings into the second environment. In other words, the liquid ring acts as a compressing agent, and performs the same function as a reciprocating piston in a hydraulic cylinder. Similar pumps are also known from DE 7009100U .
Pumps of the above type are fairly complex and expensive, by requiring rotors with a number of appropriately shaped blades to exert thrust on the operating liquid, and are of relatively poor efficiency, by operating at fairly modest liquid flow rates - normally about 2-3 m³/h. With a low flow rate, the pump tends to produce severe heating of the circulating liquid, the vapour pressure of which limits the degree of vacuum obtainable. In other words, the higher the liquid temperature, the lower the resulting vacuum.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a vacuum pump designed to provide a straightforward, low-cost solution to the aforementioned drawbacks typically associated with known pumps.
According to the present invention, there is provided a vacuum pump comprising an outer casing having at least a first opening connected to an environment in which a vacuum is to be formed; and a rotor supplied with an operating liquid, and mounted to rotate about an axis inside said casing to produce, by movement of said operating liquid, a vacuum in the environment connected to said first opening; characterized in that said rotor comprises generating means for generating a screw-shaped stream of operating liquid to draw gaseous fluid by suction through said first opening.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a side view of a vacuum pump in accordance with the present invention;
Figures 2 and 3 show, with parts removed for clarity, respective larger-scale axial sections, in perpendicular planes, of the Figure 1 pump;
Figure 4 shows a section along line IV-IV in Figure 3;
Figure 5 shows a larger-scale view of a detail of the Figure 3 pump.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figures 1 to 3 indicates as a whole a vacuum pump in accordance with the present invention.
Pump 1 substantially comprises a supporting structure 2 indicated schematically by a dash line in Figure 1; a tubular casing 3, of axis A, fitted vertically to supporting structure 2, and having an opening 4 connected to a feed conduit 6 (shown only partly in Figure 1) supplying operating liquid, in this case water, and an opening 5 connected to an environment in which a vacuum is to be produced; and a rotor 7, of axis A, mounted inside casing 3 to rotate about axis A and generate, by movement of the operating liquid, a vacuum in the environment connected to opening 5.
Casing 3 substantially comprises a cylindrical main portion 8; and a truncated-cone-shaped bottom end portion 9 decreasing in section as of main portion 8 and acting as a diffuser. End portion 9 of casing 3 is connected by an outlet conduit 10 to an operating liquid tank 11 (shown schematically by a dash line in Figure 1) preferably forming part of a recirulating and cooling circuit connecting conduit 10 to the feed conduit 6.
More specifically, main portion 8 of casing 3 is defined by four cylindrical tubular bodies 12, 13, 14, 15, which have respective top and bottom flanges 16, 17 projecting radially outwards, and are fixed coaxially and in fluidtight manner to one another by bolts along respective flanges 16, 17. More specifically, tubular body 12 is fixed in fluidtight manner to bottom end portion 9 of casing 3, and tubular bodies 13, 14, 15 are arranged successively along axis A as of tubular body 12. As shown in Figures 1 to 3, tubular bodies 13, 14 have respective openings 5, 4, from which project, respectively, a fitting 19 for attaching a conduit 21 connected to the environment in which to produce a vacuum, and a fitting 20 for attaching feed conduit 6. Tubular bodies 13, 14, 15 are substantially the same length and shorter than tubular body 12; and the top flange 16 of tubular body 15 defines a supporting and fastening surface for a known electric motor 22 powering rotor 7.
As shown in Figures 2 and 3, rotor 7 is angularly integral with an output shaft 23 of electric motor 22, having axis A and projecting inside tubular bodies 14, 15 of casing 3.
More specifically, shaft 23 extends through and is fitted to a cylindrical bushing 24 extending inside tubular body 15 and fixed to and projecting from a plate 25 gripped between bottom flange 17 of tubular body 15 and top flange 16 of tubular body 14. More specifically, shaft 23 is fitted in axially fixed, rotary manner to bushing 24 by means of two bearings, and engages a central through opening in plate 25. To prevent operating liquid leaking from tubular body 14, having opening 4, to tubular body 15, supporting electric motor 22, a first sealing ring 30 is provided between plate 25 and top flange 16 of tubular body 14, and a second sealing ring 31 is provided between shaft 23 and plate 25.
Shaft 23 has a threaded end portion 32 projecting inside tubular body 14 and screwed and tightened by a bolt 33 to a supporting member 34, of axis A, from which rotor 7 projects integrally.
As shown particularly in Figures 2, 3 and 5, supporting member 34 is housed inside tubular body 14, is substantially cup-shaped, and comprises a disk-shaped top end wall 35 having a through hole 36, of axis A, for insertion of end portion 32 of shaft 23; and a substantially cylindrical lateral wall 37, which has a number of windows 38, through which the operating liquid entering casing 3 from opening 4 flows, and which defines, at the opposite end to end wall 35, an opening 39 by which operating liquid is fed to rotor 7. More specifically, at opening 39, lateral wall 37 defines an end flange 40 projecting radially outwards and fixed by screws to an annular plate 42 fitted for rotation, with the interposition of a bushing, inside bottom flange 17 of tubular body 14.
Plate 42 defines a central opening 44 communicating with opening 39 to permit operating liquid flow to rotor 7, and has a peripheral edge 45 projecting parallel to axis A and fixed by screws to rotor 7.
An important aspect of the present invention lies in rotor 7 having a distribution conduit 50 for distributing the operating liquid fed by conduit 6 through openings 39, 44 in supporting member 34 and plate 42, and producing, as rotor 7 rotates about axis A, a screw-shaped stream of operating liquid to draw gaseous fluid, e.g. air, by suction through opening 5.
More specifically, rotor 7 extends inside tubular body 13, faces opening 5, and comprises a disk-shaped plate 51 fixed to the projecting peripheral edge 45 of plate 42, engaging top flange 16 of tubular body 13 in rotary and axially fixed manner, and from which distribution conduit 50 projects.
More specifically, distribution conduit 50 projects from plate 51 along axis A, has an elongated rectangular section extending along a diameter of plate 51, and is fixed, e.g. welded, to a lateral edge of a diametrical through opening 52 in plate 51. Opening 52 is also rectangular, decreases slightly in section from the side facing plate 42, and assumes the same shape as the section of distribution conduit 50 on the side from which this originates.
Distribution conduit 50 has an outlet 55 located close to and downstream from opening 5 in the operating liquid flow direction.
Rotor 7 also comprises two blades 53, which project from plate 51 along axis A and the whole length of distribution conduit 50, are oriented along the same diameter of plate 51, perpendicular to the diameter from which distribution conduit 50 originates, and are fixed to opposite sides of distribution conduit 50 to define, with it, a cross-shaped impeller. Blades 53 substantially provide for balancing rotor 7 as it rotates.
In actual use, the operating liquid fed into tubular body 14 of casing 3 along conduit 6 and through opening 4 flows through supporting member 34 and openings 44, 52 in plates 42, 51 into distribution conduit 50.
By force of gravity and the rotation of rotor 7, the operating liquid flows from the bottom end of distribution conduit 50 to form, in the part of casing 3 beneath opening 5 and rotor 7, a screw-shaped stream of operating liquid, which draws gaseous fluid through opening 5 by suction to produce a vacuum in the environment connected to opening 5.
The advantages of pump 1 according to the present invention will be clear from the foregoing description.
In particular, pump 1 is straightforward and cheap to produce, by not requiring, for example, a rotor with contoured blades.
Moreover, since rotor 7 substantially comprises a distribution conduit 50 rotating about axis A, pump 1 can handle relatively high operating liquid flow rates of about 200 m³/h, i.e. roughly ten times those of the liquid-ring pump described previously, thus greatly reducing in-service heating of the operating liquid by pump 1, and so greatly increasing efficiency.
Finally, operating with high flow rates, pump 1 is practically unaffected by the vapour in the incoming operating liquid.
Clearly, changes may be made to pump 1 as described and illustrated herein without, however, departing from the scope of the accompanying Claims.

Claims

A vacuum pump (1) comprising an outer casing (3) having at least a first opening (5) connected to an environment in which a vacuum is to be formed; and a rotor (7) supplied with an operating liquid, and mounted to rotate about an axis (A) inside said casing (3) to produce, by movement of said operating liquid, a vacuum in the environment connected to said first opening (5); characterized in that said rotor (7) comprises generating means (50) for generating a screw-shaped stream of operating liquid to draw gaseous fluid by suction through said first opening (5).
A pump as claimed in Claim 1, characterized in that said generating means comprise an operating liquid distribution conduit (50) extending parallel to said axis (A), having a section elongated radially with respect to said axis (A), and rotating about said axis (A).
A pump as claimed in Claim 2, characterized in that said casing (3) comprises a second opening (4) through which operating liquid is fed into said distribution conduit (50).
A pump as claimed in Claim 2 or 3, characterized in that said distribution conduit (50) faces said first opening (5), and has an outlet (55) located close to a downstream edge of said first opening (5) with reference to the flow direction of the operating liquid.
A pump as claimed in Claim 4, characterized in that said outlet (55) of said distribution conduit (50) is located downstream from said first opening (5) in the flow direction of the operating liquid.
A pump as claimed in any one of Claims 2 to 5, characterized in that said rotor (7) comprises a disk-shaped plate (51) fitted inside said casing (3) to rotate about said axis (A), and defining a third opening (52) for the passage of the operating liquid; and in that said distribution conduit (50) projects from a diameter of said plate (51), and communicates with said third opening (52).
A pump as claimed in Claim 6, characterized in that said third opening (52) and the section of said distribution conduit (50) are rectangular and elongated along the same diameter of said plate (51).
A pump as claimed in Claim 6 or 7, characterized in that said distribution conduit (50) extends from a lateral edge of said third opening (52) of said plate (51); and in that said third opening (52) decreases in section towards said distribution conduit (50).
A pump as claimed in any one of Claims 6 to 8, characterized in that said rotor (7) comprises two blades (53), which project from said plate (51) along the whole length of said distribution conduit (50), are oriented along the same diameter of said plate (51), perpendicular to the diameter from which said distribution conduit (50) originates, and are fixed to opposite sides of the distribution conduit (50) to define, with it, a cross-shaped impeller.
A pump as claimed in any one of the foregoing Claims, characterized in that said casing (3) and said rotor (7) are coaxial; and in that said axis (A) extends vertically.
A pump as claimed in any one of the foregoing Claims, characterized in that said rotor (7) is connected integrally to a free end portion (32) of an output shaft (23) of an electric motor (22) fixed to said casing (3).