Liquid ring vacuum pump

Abstract

Liquid ring vacuum pump (1), comprising: a fixed body (2) defining within it a pumping chamber (3) and provided with an intake conduit (4) and an outlet conduit (5) put in fluid communication with the pumping chamber (3); an impeller (6) provided with vanes and eccentrically housed in said pumping chamber (3); a drive shaft (7) extending between a first end (7a), located at the pumping chamber (3) and to which said impeller (6) is coupled, and a second end (7b) coming out of the body (2); a fixing device (10) for fixing the impeller (6) to the drive shaft (7), comprising: − a threaded element (11) screwed into a corresponding seat obtained in the first end (7a) of the drive shaft (7); − an annular flange (12) abutting against the impeller (6) and reversibly coupled thereto; a spacer device (13) interposed between the fixing device (10) and the drive shaft (7).

Description

[0001] DESCRIPTION

[0002] LIQUID RING VACUUM PUMP

[0003] Technical field

[0004] The present invention relates to a liquid ring vacuum pump.

[0005] Background art

[0006] As is well-known, a liquid ring vacuum pump is a machine that is used to transport substances in the gaseous state in conditions of absolute pressure lower than ambient pressure. The field of application of the vacuum pump can vary from emptying of storage tanks, to the removal and recovery of gases during processes that produce them, in the food, pharmaceuticals, chemicals, waste processing, etc., industries.

[0007] Liquid ring vacuum pumps have already been on the market for many decades. As is well-known, they consist of a cylindrical compartment inside which a radial vane impeller rotates, the rotating motion of which ensures the formation of a liquid layer (liquid ring) at the wall of the compartment, due to the presence of an operating or sealing liquid previously introduced into the rotation compartment of the impeller. Since the impeller is placed in a non-central (eccentric) position, variable-volume chambers (delimited by the impeller vanes) are formed, in which the gas to be processed passes and is compressed.

[0008] In this context, a key aspect of the liquid ring vacuum pumps is the axial adjustment and the fixing of the impeller. The prior art is divided primarily into three solutions:

[0009] - the first provides for inserting calibrated shims behind the impeller hub to obtain the axial positioning, after which the impeller is tightened onto the shaft using a normal screw;

[0010] - the second provides for use of an axial adjustment bolt that is screwed on one side onto the shaft head and on the other locks the cap onto the impeller by means of a nut;

[0011] - the third solution provides for interference fitting of the impeller onto the shaft. Rings known as “tolerance rings” are sometimes used. The prior art brings with it numerous unresolved problems in the system of axial adjustment and fixing of the impeller.

[0012] In the first place, there is a need to mount and dismount the impeller several times in order to be able to measure the axial clearance. The practice of the competitors for axial positioning is as follows:

[0013] I. Mount the impeller with a nominal shim behind the hub

[0014] II. Measure the axial clearance between plate (element) and impeller

[0015] III. Remove the impeller (this has an extremely precise coupling on the shaft and therefore requires the use of a dedicated extractor and a considerable amount of time)

[0016] IV. Insert suitable shims behind the impeller hub

[0017] V. Remount the impeller

[0018] VI. Measure to confirm the correct axial clearance

[0019] VII. Tighten the fixing screws to complete assembly

[0020] This procedure requires a huge amount of time to be spent.

[0021] In the case of a fixing system using an adjustment bolt or adjustable screws, in view of the extent of the clearances to be adjusted (in the order of ±0.1 mm), the pitch of the screws used does not allow precise adjustment, since they all have a large thread pitch (e.g. pitch 1.5 mm). Furthermore, the screw and locknut (or locking cover) system is difficult to use since, at the moment of final fixing, slips occur that take the clearance outside the permitted tolerance.

[0022] Lastly, the use of an interference system between hub and shaft requires the use of complex systems, for example heating of the impeller or a hydraulic press to force the impeller into its seat. In both cases, adjustment of axial clearance is highly complex, since there is no mechanical abutment that determines the end point of insertion of the impeller onto the shaft.

[0023] Disclosure of the invention

[0024] In this context, the technical task underlying the present invention is to propose a liquid ring vacuum pump which overcomes the drawbacks in the prior art as described above.

[0025] In particular, an object of the present invention is to provide a liquid ring vacuum pump which allows axial adjustment of the impeller on the shaft that is quicker than the known solutions.

[0026] Another object of the present invention is to propose a liquid ring vacuum pump in which it is not necessary to remove the impeller from the shaft in order to be able to perform axial adjustment thereof.

[0027] Another object of the present invention is to propose a liquid ring vacuum pump on which measurement of the axial clearance is simpler and more immediate than in the known solutions.

[0028] The stated technical task and the specified objects are substantially achieved by a liquid ring vacuum pump, comprising: a fixed body, defining within it a pumping chamber and provided with an intake conduit and an outlet conduit put in fluid communication with the pumping chamber; an impeller provided with vanes and eccentrically housed in said pumping chamber; a drive shaft extending between a first end, located at the pumping chamber and to which said impeller is coupled, and a second end coming out of the body for connection to motorised means; a fixing device for fixing the impeller to the drive shaft, comprising:

[0029] - a threaded element screwed into a corresponding seat obtained in the first end of the drive shaft;

[0030] - an annular flange abutting against the impeller and reversibly coupled thereto; a spacer device interposed between the fixing device and the drive shaft.

[0031] In accordance with one embodiment, the fixing device has the threaded element at one end and the annular flange at an opposite end.

[0032] In accordance with one embodiment, the fixing device is monolithic.

[0033] In accordance with one embodiment, said annular flange and said impeller are coupled by means of a locking element inserted into corresponding holes obtained, respectively, in the annular flange and in the impeller.

[0034] Preferably, the annular flange has a first plurality of first through holes and the impeller has a second plurality of second holes, said annular flange and said impeller being mutually arranged so that at least some of the first holes are facing at least a part of the second holes.

[0035] Preferably, the first holes are in an elongate form with a curvilinear shape.

[0036] In accordance with one embodiment, the fixing device comprises a first portion and a second portion with a different diameter, the threaded element projecting from the first portion, the second portion having the annular flange, said impeller comprising a shaped through hole having a first section and a second section with different diameters and adapted to receive, respectively, the first portion and the second portion of the fixing device.

[0037] Preferably, the fixing device comprises a third portion interposed between the first and the second portion and having an intermediate diameter, said shaped through hole having a third section with a diameter such as to receive said third portion.

[0038] In accordance with one embodiment, the fixing device extends between the annular flange and the threaded element with a progressive reduction in cross-section area.

[0039] Brief description of drawings

[0040] Further characteristics and advantages of the present invention will become more apparent from the following indicative and therefore nonlimiting description of a liquid ring vacuum pump, as illustrated in the appended figures, in which:

[0041] - Figure 1 shows a perspective view of a liquid ring vacuum pump, according to the present invention;

[0042] - Figure 2 shows a cross-sectioned view of the pump of Figure 1 ;

[0043] - Figure 3 shows an exploded view of a part (pump body) of the pump of figure 1 ;

[0044] - Figure 4 shows a part (impeller) of the pump of Figure 1 , in a front view; - Figure 5 shows a cross-sectioned view of the impeller of Figure 4 according to the line B-B;

[0045] - Figure 6 shows an enlarged view of a part (detail C) of the view of Figure 5;

[0046] - Figure 7 shows a part (impeller and fixing device) of the pump of Figure 1 , in a front view;

[0047] - Figure 8 shows a cross-sectioned view of the part of Figure 7 according to the line D-D.

[0048] Detailed description of preferred embodiments of the invention

[0049] With reference to the figures, the number 1 indicates the liquid ring vacuum pump that is the subject-matter of the present invention.

[0050] The pump 1 comprises a fixed body 2. The body 2 is shaped so as to define within it a pumping chamber 3. The body 2 is provided with an intake conduit 4 and an outlet conduit 5 put in fluid communication with the pumping chamber 3. Their task is respectively to supply a working fluid thereto and to move it away therefrom, as known.

[0051] The pump 1 comprises an impeller 6, provided with vanes, which operates in the pumping chamber 3. In particular, the impeller 6 is fitted onto a drive shaft 7 and is arranged eccentrically in the pumping chamber 3. Preferably, the impeller 6 is fitted onto the drive shaft 7 by means of a key. The impeller 6 and its function are known in themselves for a liquid ring pump.

[0052] The drive shaft 7 extends between a first end 7a and a second end 7b. The first end 7a is located at the pumping chamber 3 and is coupled with the impeller 6. The second end 7b comes out of the body 2. The drive shaft 7 can be connected to motorised means (which is not part of the pump described here) or be directly the shaft of the motorised means. The drive shaft 7 therefore transmits the drive torque to the impeller 6, which suctions the working fluid from the intake conduit 4 and sends it towards the outlet conduit 5.

[0053] As is well-known, the liquid ring vacuum pumps are volumetric machines that produce a vacuum during suction or compression during delivery.

[0054] These exploit two key points for operation: the eccentricity of the impeller relative to the body, added to the constant introduction of the service liquid into the pumping chamber, thus creating a centrifuged fluid ring on the outer wall of the chamber itself and therefore of the variable-volume compartments between the vanes of the impeller. These compartments are selectively put in communication with suction and delivery by means of known solutions.

[0055] Opportunely, the pump 1 comprises an inlet for the service liquid to enter into the pumping chamber 3.

[0056] In the embodiment shown, the fixed body 2 comprises a support member 21 and a closing member 22 reversibly coupled with each other. In more detail, the closing member 22 comprises a closing flange 23, with which the aforesaid intake and outlet conduits 4, 5 are associated.

[0057] The support member 21 , on the other hand, comprises a base plate 24 and a tubular wall 25 extending perpendicular to and at the perimeter from said plate to define the side wall 3a of the pumping chamber 3.

[0058] The base plate 24 is also provided with a circular opening 26 that allows passage of the drive shaft 7. At such opening, a mechanical seal 27 arranged to prevent leakage of the pressurised fluid from the pumping chamber s is conventionally used.

[0059] There is a distribution plate 28 interposed between the support member 21 and the closing member 22. The distribution plate 28 acts in abutment on an end edge 25a of the tubular wall 25, so as to define the pumping chamber 3.

[0060] Preferably, the distribution plate 28 comprises at least one inlet opening 28a for entry of the working fluid from the intake conduit 4 into the pumping chamber 3 and an outlet opening 28b for exit of the pumped fluid from the pumping chamber 3 into the outlet conduit 5.

[0061] Advantageously, such distribution plate 28 has a flexible valve 29 in the outlet openings 28b that allows the outlet area of the pumped fluid to be divided as a function of the intake pressure of the machine.

[0062] Therefore, the base plate 24 is indicated as a rear part of the body 2, in particular of the pumping chamber 3, because it is external to and facing the second end of the drive shaft 7, and therefore on the back of the pump. In contrast, the distribution plate 28 is indicated as a front part, because it is facing the front part of the pump 1 , i.e. the closing member 22.

[0063] Since this machine is volumetric, its performance is obtained by limiting, as far as possible, the passage of gas between one compartment and the adjacent ones. In order to make this passage more difficult, the service liquid is used as an insulating element, together with the reduced axial tolerances between impeller 6 and base plate 24 (rear part) and between impeller 6 and distribution plate 28 (front part). The order of magnitude of the axial tolerance to obtain acceptable performance is indicatively 0.3% of the axial length of the impeller seat.

[0064] The invention proposed here is centred on the fixing between the impeller 6 and the drive shaft 7 which, as will become clearer from the description that follows, simultaneously allows the rapid axial adjustment of the position of the impeller 6 and fixing of the impeller 6 to the drive shaft 7, with a screw-locking system.

[0065] The pump 1 comprises a fixing device 10 for fixing the impeller 6 to the drive shaft 7.

[0066] The fixing device 10 comprises a threaded element 11. The threaded element 11 is screwed into a corresponding seat obtained in the first end 7a of the drive shaft 7.

[0067] In particular, the threaded element 11 extends protruding from the rest of the fixing device 10.

[0068] The fixing device 10 further comprises an annular flange 12 abutting against the impeller 6 and reversibly coupled thereto.

[0069] The function of the coupling between the annular flange 12 and impeller 6 is to avoid decoupling between the impeller 6 and the drive shaft 7 and to solidly constrain the fixing device 10 to the impeller 6 in an axial direction. In other words, it serves to keep the impeller 6 in the axial position.

[0070] The pump 1 comprises a spacer device 13 interposed between the fixing device 10 and the drive shaft 7.

[0071] In the embodiment shown, the spacer device 13 comprises one or more annular shims.

[0072] In another embodiment, the spacer device 13 is a perforated cylindrical element. For example, the cylindrical element is made of plastic material. The proposed invention therefore allows a more rapid axial adjustment of the impeller 6 on the drive shaft 7, since the spacer device, which is already known, is positioned directly on the head of the drive shaft 7 (i.e. at the first end).

[0073] Preferably, the fixing device 10 has the threaded element 11 at one end and the annular flange 12 at an opposite end.

[0074] Preferably, the fixing device 10 extends between the annular flange 12 and the threaded element 11 with a progressive reduction in cross-section area.

[0075] In summary, the fixing device 10 connects the impeller 6 to the drive shaft 7 by being interposed between them. The impeller 6 is connected to the fixing device 10 by means of the annular flange 12 and, in turn, the fixing device 10 is connected to the drive shaft 7 by means of the threaded element 11 .

[0076] In the preferred embodiment, the fixing device 10 is monolithic. This means that it is and acts as the sole interconnection element between the impeller 6 and the drive shaft 7, regardless of whether it is made in a single piece or in several parts solidly constrained to each other.

[0077] In other words, it is not made of several, separate elements that are interposed between impeller 6 and drive shaft 7. Furthermore, it does not cooperate with further elements (of substantial function, and therefore excluding any fixing elements, seals, etc.) interposed between it and the impeller 6 or the drive shaft 7. Preferably, the annular flange 12 and the impeller 6 are coupled by means of locking elements 14 inserted into corresponding holes obtained, respectively, in the annular flange 12 and in the impeller 6.

[0078] In particular, the annular flange 12 has a first plurality of first through holes 15. The impeller 6 has a second plurality of second holes 16.

[0079] The annular flange 12 and the impeller 6 are mutually arranged so that at least several of the first holes 15 are facing at least one part of the second holes 16 in order to allow insertion of the locking elements 14.

[0080] In the embodiment shown, the first holes 15 are in an elongate form with a curvilinear shape. In other words, they have the shape of mechanical slots with a curvilinear extension.

[0081] In particular, the first elongated holes 15 are circumferentially distributed and are equally distanced from each other.

[0082] The presence of the slots (first elongated holes) on the annular flange 12 and of a sufficient number of holes on the impeller 6 always allows a sufficient number of locking elements 14 to be inserted, whatever the radial position between the impeller 6 and the fixing device 10, in particular the annular flange 12.

[0083] Furthermore, the abutment also acts as a resting section between the impeller 6 and the fixing device 10 so that, once the locking elements 14 have been inserted into the first holes 15 and tightened by means of the threaded second holes 16 present on the hub of the impeller 6, the fixing device 10 and the impeller 6 become an integral element.

[0084] In the preferred embodiment, there are three elongated first holes 15 and at least six second holes 16, alternately divided into two groups of three for coupling with the first three holes 15. In this manner, the coupling is easily ensured, independently of the direction.

[0085] In accordance with one embodiment, shown in the drawings, the fixing device 10 is advantageously made as a monobloc body. Such monobloc body extends between a first end having the annular flange 12 and a second end having the protruding threaded element 11 . In other words, the aforementioned two elements are positioned on opposite sides of the fixing device 10.

[0086] In an alternative embodiment, the fixing device 10 is made of several parts.

[0087] In accordance with one embodiment, shown in the drawings, the impeller 6 comprises a shaped through hole 61 to house the fixing device 10.

[0088] In particular, the fixing device 10 comprises a first portion 101 and a second portion 102 with different diameters. The threaded element 101 protrudes from the first portion 101. The second portion 102 has the annular flange 12. The shaped through hole 61 consequently has a first section 62 and a second section 63, with different diameters and shaped to house, respectively, the first portion 101 and the second portion 102 of the fixing device 10.

[0089] The diameter of the second portion 102 is higher than the diameter of the first portion 101. Equally, the diameter of the second section 63 is higher than the diameter of the first section 62, so that the second section 63 effectively defines the abutment for the annular flange 12.

[0090] Preferably, the first portion 101 has a diameter consistent with the diameter of the first end 7a of the drive shaft 7, except for a tolerance that allows easy insertion. On this diameter, the appropriate key slot for transmission of motion lies on the impeller 6.

[0091] Preferably, a third portion 103 interposed between the first and the second portion 101 , 102 is present. The diameter of the third portion 103 is intermediate between the diameters of the two portions 101 , 102.

[0092] Equally, the shaped through hole 61 comprises a third section 64, intermediate between the first section 62 and the second section 63. The diameter of the third section 64 is intermediate between the diameters of the two sections 62, 63.

[0093] The function of the third portion 103 is therefore to centre the fixing device 10 on the impeller 6, since it is the only precise diameter (therefore with narrow tolerance) between the first portion 101 and the second portion In one embodiment, the third portion 103 has a gasket seat, adapted to insulate the shaft 7 and the key against potential contamination with the pumped fluid or gas.

[0094] In other words, the fixing device 10 and thus also the shaped through hole 61 have three different sequential parts with different decreasing diameters.

[0095] Preferably, the impeller 6 comprises a hub 60, which is the part of the impeller 6 that couples with the fixing device 10. In particular, the shaped through hole 61 that houses the fixing device 10 is obtained in the hub 60.

[0096] In accordance with the present invention, the pump 1 is installed in the following manner (considering the body 2 and the drive shaft 7 as already assembled):

[0097] 1 . insertion of the key onto the drive shaft 7;

[0098] 2. insertion of the impeller 6 onto the drive shaft 7 (a radial constraint is created between shaft and impeller);

[0099] 3. placing of the impeller 6 in abutment on the rear face (base plate 24) of the support member 21 , measurement of the axial clearance between the head of the drive shaft 7 and the resting surface of the fixing device 10 on the impeller 6 (maximum diameter);

[0100] 4. measurement of the nominal distance between the resting surface of the impeller 6 (maximum diameter) and the resting surface of the shims (minimum diameter) in the fixing device 10;

[0101] 5. calculation of the pack of annular shims 13 to be inserted between the head of the drive shaft 7 and the resting surface of the shims in the fixing device 10 (considering the axial clearance to be maintained between the impeller 6 and the rear face of the support member 21 );

[0102] 6. insertion of the annular shims 13 into the central cavity of the impeller 6;

[0103] 7. torque tightening of the fixing device 10 by means of the protruding threaded element 11 positioned in the front part, inserting it into the corresponding threaded seat present in the head of the drive shaft

[0104] 7

[0105] 8. tightening of the locking elements 14 between the fixing device 10 and the hub of the impeller 6.

[0106] In this manner, with the operations described here above, the impeller 6 has been positioned and tightened in a single step, without needing to be removed after axial measurement, which is what happens in the known solutions.

[0107] Possibly, a mechanical seal 27 is assembled on the hub of the impeller 6 before insertion of the drive shaft 7.

[0108] The characteristics of the liquid ring vacuum pump according to the present invention emerge clearly from the above description, as do the advantages.

[0109] In particular, the solution proposed for the fixing device for fixing the impeller to the drive shaft allows the annular shims to be positioned directly on the head of the drive shaft. Consequently, the impeller can be positioned and tightened in a single step, without needing to be removed after axial measurement.

[0110] Furthermore, the embodiment with elongated holes (mechanical slots) on the fixing device allows easy and rapid adjustment, without the need for specific angular positioning of the impeller with respect to it.

[0111] Furthermore, the proposed fixing device defines a solution that becomes monolithic with the impeller, giving the advantages listed above while still remaining compact.

Claims

CLAIMS1. A liquid ring vacuum pump (1 ), comprising: a fixed body (2) defining within it a pumping chamber (3) and provided with an intake conduit (4) and an outlet conduit (5) put in fluid communication with the pumping chamber (3); an impeller (6) provided with vanes and eccentrically housed in said pumping chamber (3); a drive shaft (7) extending between a first end (7a), located at the pumping chamber (3) and to which said impeller (6) is coupled, and a second end (7b) coming out of the body (2); a fixing device (10) for fixing the impeller (6) to the drive shaft (7), comprising:- a threaded element (11 ) screwed into a corresponding seat obtained in the first end (7a) of the drive shaft (7);- an annular flange (12) abutting against the impeller (6) and reversibly coupled thereto; a spacer device (13) interposed between the fixing device (10) and the drive shaft (7).

2. The pump (1 ) according to claim 1 , wherein the fixing device (10) has the threaded element (11 ) at one end and the annular flange (12) at an opposite end.

3. The pump (1 ) according to claim 2, wherein the fixing device (10) is monolithic.

4. The pump (1 ) according to any one of the preceding claims, wherein said annular flange (12) and said impeller (6) are coupled by means of a locking element (14) inserted into corresponding holes (15, 16) obtained, respectively, in the annular flange (12) and in the impeller (6).

5. The pump (1) according to claim 4, wherein the annular flange (12) has a first plurality of first through holes (15) and the impeller (6) has a second plurality of second holes (16), said annular flange (12) and said impeller (6) being mutually arranged so that at least some of the first holes (15) arefacing at least a part of the second holes (16).

6. The pump (1) according to claim 5, wherein the first holes (15) are in an elongate form with a curvilinear shape.

7. The pump (1 ) according to any one of the preceding claims, wherein said fixing device (10) comprises a first portion (101 ) and a second portion(102) with different diameters, the threaded element (11 ) projecting from the first portion (101 ), the second portion (102) having the annular flange (12), said impeller (6) comprising a shaped through hole (61 ) having a first section (62) and a second section (63) with different diameters and adapted to receive, respectively, the first portion (101 ) and the second portion (102) of the fixing device (10).

8. The pump (1 ) according to claim 7, wherein said fixing device (10) comprises a third portion (103) interposed between the first and the second portion (101 , 102) and having an intermediate diameter, said shaped through hole (61 ) having a third section (64) with a diameter such as to receive said third portion (103).

9. The pump (1 ) according to any one of the preceding claims, wherein the fixing device (10) extends between the annular flange (12) and the threaded element (11 ) with a progressive reduction in cross-section area.

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