EP1247994B1

EP1247994B1 - Centrifugal pump with adjustment of the axial and radial clearances without opening the pump body

Info

Publication number: EP1247994B1
Application number: EP02076079A
Authority: EP
Inventors: Umberto Cambiaghi
Original assignee: Cambiaghi Umberto
Current assignee: Cambiaghi Umberto
Priority date: 2001-03-21
Filing date: 2002-03-20
Publication date: 2004-04-14
Anticipated expiration: 2022-03-20
Also published as: ITMI20010592A0; ITMI20010592A1; DE60200359D1; EP1247994A2; ES2220873T3; TR200401664T4; DE60200359T2; EP1247994A3; ATE264459T1

Abstract

A centrifugal pump comprises a pump body or casing (2), a rotor (5) connected to a shaft (4), an upper removable cover (3), with the seal between the pump body (2) and the rotor (5) being ensured by rings (10, 11), attached to the casing (2), facing rings (25), attached to the rotor (5), which are made to rotate with it. According to the invention, both the fixed sealing rings (10, 11) and the bearings for supporting the rotating part of the pump (8, 9; 8bis, 9bis) are assembled on two removable side covers (6, 7) arranged at the two sides of the pump body (2). <IMAGE>

Description

The present invention refers to centrifugal pumps and in particular to a simplified and dismountable centrifugal pump structure which allows a somewhat easier and more cost-effective realisation, assembly and maintenance.
In general, centrifugal pumps are machines in which energy is transferred from the machine to the fluid through a rotor which moves with respect to the fluid. Their structure comprises a static part and a moving part: an outer casing which contains the rotor fitted on a shaft which is moved, by means of a rigid joint, by a motor. In general, between the two parts sealing members are interposed which carry out their function between flat or cylindrical interfacing surfaces, in motion relative to each other. To increase the seal and to reduce the friction forces present, many types of pump of the prior art are generally equipped with auxiliary lubrication devices of such surfaces distributing a lubrication fluid in the gaps between the interfacing gaskets.
Such lubrication devices are the source of substantial drawbacks, be it of the environmental type due to the losses and disposal of the lubrication fluids, be it of mechanical yield of the machine due to fluid leakages, or be it finally for the complicatedness and the greater size of the machine.
Centrifugal pump structures without auxiliary lubrication devices and with a seal of the radial type between flat surfaces are known from patent USA 6,004,094 which represents the closest prior art and from patents USA 4,242,039, 4,501,530 and 4,913,619. Such centrifugal pump structures are, however, quite complex and have difficulties in their realisation, assembly, maintenance and adjustment.
Pumps with interfacing coaxial sealing rings, frontally or concentrically, directly on the pump body and on the rotor are not without drawbacks. These assemblies involve complex and precise working of the pump body and, in the case of seizure or uncontrolled wearing through time, irreparable damage to the body of the pump. Sealing rings of the conventional type are subject to wear during their lifetime, which means an increase in the clearances between the seals with a significant worsening in yield and a substantial increase in energy consumption.
The present invention refers more precisely to a centrifugal pump with a dismountable structure which is a good deal simpler and easier to realise, assemble, maintain and adjust. It is, moreover, equipped with an innovative bearing fluxing system, without the use of piping and adjustment valves.
The pump according to the invention is defined, with its essential characteristics, in the first claim, whereas the dependent claims define preferred embodiments and improvements of the invention.
To illustrate the characteristics and the advantages of the present invention with greater clarity, it is described with reference to some typical embodiments thereof shown in figures 1, 2, 3, 4, 5, 6 and 7 as an example and not for limiting purposes.
In figure 1A, B an embodiment of the pump is shown according to an axial section view (figure 1A) and a schematic front view (figure 1B), respectively.
Figure 2 shows in its main components the structure of the pump according to the view of figure 1, but in an "exploded" configuration to illustrate its types of assembly and of access to the moving parts.
Figure 3 again partially shows the pump according to the view of figure 1, for the detail of the fluxing of the bearings and of the mechanical seal which constitutes a preferred embodiment of the pump according to the invention.
Figure 4 again shows the pump according to the view of figure 1, for the detail of a different structure of side cover aimed at limiting possible axial slipping, which constitutes an alternative embodiment of the pump according top the invention.
In figure 5 a special embodiment of the pump according to the invention is illustrated for application with liquids containing abrasive particles.
Figures 6, 7 are details in section view which illustrate a system for adjusting the clearances between rotor and sealing rings.
As illustrated in figures 1 to 5, the centrifugal pump according to the invention comprises support feet 1 integral with the pump body 2, which contains a rotor 5 fitted onto a shaft 4 through a grooved profile 20 or, alternatively, through a key, which does not restrict the rotor in the axial direction. The shaft 4 is connected to its motor - not shown in the figures for the sake of simplicity - with a per se known joint, indicating only the slot 21 for inserting, for example, a coupling key. The casing or pump body 2 foresees from the two sides a fluid intake IN and and a pumped fluid discharge OUT, on the left and right-hand side in figure 1B, respectively. In the upper part of figure 1 an upper removable cover 3 of the casing 2 is shown, with screws for attaching to the casing itself.
From the left and right-hand side of the pump body, in the plane of the drawing of figure 1A, two funnel-shaped side covers 6, 7 are respectively assembled, upon which the lubricated bearings or bushings 8, 9 are respectively assembled. Upon the same side covers 6, 7 are also respectively assembled sealing rings 10, 11 of the fixed part connected to the pump body, respectively facing the sealing rings 25 connected to the rotor 5 and rotating with it. The shaft 4, the rotor 5 and its sealing rings 25 therefore constitute the rotating part of the pump.
It is possible for the rotor to be fitted without rings 25 and can work in direct opposition to the rings 10, 11 of the body with worked surfaces.
The interfacing sealing rings 10, 11, 25 be they fixed or rotating can be realised with various materials, which are preferably resistant to wear and with a low friction coefficient, for example with resin, containing possible additional fillers, silicon carbides, ceramic, metallic alloys.
The side covers 6, 7 are preferably equipped with spokes 16 and 15, respectively, which allow the areas of the lubricated bearings 8, 9 to be supported effectively, avoiding their cantilevered support, as in conventional pumps. The spokes are integral with the rings 17, 17a, upon which the wear rings 10, 11 are assembled.
The axial division between body 2 and upper cover 3 of the pump can be realised, in a traditional manner, according to a plane passing by the line of axis 12 or else, according to the embodiment shown in figures 1B, 2, displaced upwards according to a plane 13 parallel to the previous one, to be able to attach and lift the rotor 5 and remove it from the pump body 2, without involving the other parts of the pump.
The restriction in position of the rotor 5 in the axial direction is realised with two distance rings 23, 24 - left and right respectively - divided into two halves and fixed to the rotor by means of screws, and arranged on the two sides of the widening of the groove 20 which thus hold the shaft 4 in position axially, whereas its setting and the absorption of the forces in the axial direction is the function of members which are described hereafter.
At the two side ends of the casing 2 the two covers 6, 7 are equipped with devices both for adjusting the axial clearances and for absorbing the forces in such a direction. For the adjustment of the axial clearances 22 between the front rings 10, 11, 25 shown more clearly in figure 5, a plurality of screws 14, 19 are foreseen, for the right 7 and left 6 cover respectively, of which one of the screws 14 is shown in the enlarged detail of figure 1. The right cover 7, just like the left cover 6, is shaped in its outer face with a frustum of cone surface upon/from which the ends of the screws 14, 19 are pushed/withdrawn, respectively, in the radial direction, such a drive translating into an axial displacement of the covers 6, 7 inwards, according to the principle of the inclined plane.
On the other hand, to distance the covers axial screws can be used, 14bis in the right-hand part and 19bis in the left-hand part, respectively, which abut against the casing 2, operate in an axial direction and cause the distancing of the side covers. For simplicity's sake, this detail is shown only in figure 5.
Such an axial displacement of the two covers 6, 7 closens or distances the front rings 10, 11, 25 and adjusts their clearance 22. As an example, in the schematic side view of figure 1B, four screws 19 are foreseen separated by 90° from each other.
The seal and the locking of the two covers is completed with the mechanical seal on the right. It consists of a cover 18, smaller than and concentric with the cover 7, which is fixed to it with screws. Inside of it, the small cover 18 carries a sealing ring 41 and a compressed spring 42 which rests on one side against the inner face of the ring 41 and on the other side against a shoulder of the shaft 4. The spring 42 is compressed and pushes the shaft towards the left in the plane of the drawing and pushes the sealing ring 41 towards the right. On the other side, the push of the spring 42 is counteracted with a counter push by the cover 6 which, by means of the ring 10, compresses said spring and ensures the seal.
In figure 2 the embodiment of the pump of figure 1 is illustrated, but in an "exploded" configuration. The ways of assembling and accessing the moving parts are extremely simplified. In the case in which one wishes to remove the mobile members of the pump, it is indeed sufficient to disassemble the covers 6 and 7 and withdraw the shaft 4 from the side opposite to the joint with the motor; the replacement of the sealing rings and of the sliding bearings is possible without disassembly the upper cover 3. Only if one also wishes to intervene on the rotor 5 does the upper cover have to be removed and the rotor be withdrawn from above.
Figure 3 shows a preferred embodiment of the pump according to the invention, in which the fluxing of the bearings and the mechanical seal are realised by withdrawing fluid from the pump intake. In figure 3 the fluxing system from the side of the left-hand cover 6 is illustrated, which is also applied from the right-hand side of the cover 7 in a symmetrical manner. In the wall of the left-hand cover 6 with a funnel configuration towards the rotor a series of holes 31 is realised which put the intake IN space upstream of the rotor 5 in communication with the chamber 34 of the bearing 8; on the right-hand side, however, there is the bearing 9.
From the main intake 29 a part is thus deviated as fluxing stream 30 which penetrates into the holes 31 and crosses fluxing channels 32 made in the bearing 8 and comes out as fluxing 33 between the shoulder of the bearing 8 and the distance ring 24.
The same fluxing system realised on the cover 7 cools and lubricates not just its bearing 9, but also the seal 18, 41, 42.
Figure 4 illustrates an alternative embodiment of the pump according to the invention in which a different side cover structure is adopted to control the possible axial sliding of the rotor 5 and to push the seal against the second cover 18 and to compress the spring 42.
On the shaft 4, to the left of the rotor 5 in the plane of the drawing, a ringed widening 28 is realised or fitted, upon which the rotor itself abuts.
The member for controlling axial sliding consists of a cover 27, symmetrical to the small cover 18 and concentric with the cover 6, to which it is fixed with screws. Inside of it the cover 27 carries a sealing disk 26 which locks the shaft 4 and keeps it in position with the rotor 5. The disk 26 is realised with analogous materials and finishings to those of the sealing rings 10, 11, 25.
With this solution the axial sliding only of the shaft is limited, whereas the rotor is not locked axially on the shaft itself, and its axial sliding is limited by the wear rings in the areas 22.
Figure 5 illustrates a special embodiment of the pump according to the invention for its use with liquids containing significant amounts of abrasive particles. In such conditions these abrasive particles in a short time can ruin the sliding bearings lubricated with the liquid itself, as in the embodiments shown in figures 1 to 4.
In this special embodiment the sliding bearings 8, 9 of the previous figures are eliminated and, in their place, it is foreseen to support the rotating part of the pump with two rolling bearings 8bis, 9bis, lubricated through grease/oil, assembled on the outside of two parts of the casing on two support boxes 6bis, 7bis, analogous to the small covers 18 and 27 of figure 4 and assembled on the side covers 6, 7. For the sake of simplicity of illustration such support boxes are shown of the type for lubrication of the bearings with grease.
Also with this solution the axial pushes are borne by the rings 10, 11 assembled on the side covers, just as are also the rolling bearings, which, on the other hand, in traditional pumps are assembled on the body of the pump. Such a solution therefore allows simplified assembly, maintenance and adjustment.
Also with rolling bearings the same adjustment of the clearances between the rings 25 of the rotor 5 and the sealing rings 10, 11 is possible without opening the pump. One only has to act upon the radial screws 14, 19 to reduce the clearances and upon the axial screws 14bis, 19bis to increase them.
As shown in figure 5, the rotor 5 is rotatably connected to the shaft 4, with a key or else a grooved profile. Its axial sliding on the shaft is locked with the stop 50 in one direction, and in the opposite direction by the ring in two halves 51 and by the whole ring 52.
With reference to the details of figures 6 and 7, for the adjustment of the clearances between the rotor 5 and the sealing rings 10, 11 (with the pump inactive) an axial adjustment screw 53 engages which, resting upon the face F, pushes the shaft 4 towards the right in the plane of figure 5, screwing into the threaded hole 53a of the cover 6.
To pull the rotor in the opposite direction, after having removed the pushing screw 53 from its threaded hole 53a, a threaded rod 54 with a smaller diameter than the hole 53a of the screw 53 screws into the threaded hole 54a of the shaft 4, and with a nut 55 screwed onto it and in contact with the cover 6 of the box 6bis the rotor is pulled towards the left in the plane of the drawing. With a dial gauge, after having detected the total traverse of the rotor between the wear rings 10, 11 of the body displacing it axially in the two directions, it can be positioned precisely at the centre point of the two rings of the body. The axial pushes are reduced and are not capable of making the shaft 4 slide inside the bearings; in any case they can be supported by the rings 10, 11.
As an alternative to the solution of locking the rotor 5 on the shaft 4 in the axial direction with a stop and opposing rings, the rotor can be left free to slide in the axial direction. In such a case, the axial pushes are transferred onto the rings 10, 11 and the rotor centres itself by the intake return flow which passes through the clearances between rotor and rings. The shaft 4 is thus freed completely from the axial pushes.
As can be seen from the illustrated embodiments, the centrifugal pump according to the invention has substantial advantages with respect to pumps of the state of the art.
The pump according to the invention allows access to and adjustment of its inner parts with extreme ease. All of the inner parts can be accessed without removing the motor and the piping. The setting of the clearances 22 between the radial sealing rings can be carried out from the outside by axially adjusting the two side covers 6, 7 without even opening the pump. The possibility of axially displacing the side covers with micrometric adjustments allows the clearances 22 to be adjusted with extreme precision, which cannot be obtained with traditional pumps, to obtain high energy yields, for the consequent reduction in leakages between the rings.
The pump is quite easy to construct and requires less precision treatments than those required by traditional pumps with an axially divided casing. Especially the embodiment with out-of-axis division of the size of the thickness of the rotor 5, as indicated with the cover 3, there is a better resistance of the pump body 2 to the internal pressures and a better seal in the joining plane between body and cover. The axis line, moreover, is much easier to realise since it only works on one diameter and on whole circles, whereas in traditional pumps the axis line generally requires working on various diameters and is divided in two halves.
The axial adjustment system of the side covers 6, 7 with the screws 14, 19, 14bis, 19bis not only allows the clearances to be adjusted with the pump inactive, but also allows such screws to be unscrewed and the rotation of the so-called stuffing box and the bearings 8, 9 so as to be able to use the less worn upper part, thus prolonging the lifetime of the bearings and reducing the number of interventions to replace the bearings. Such a replacement, moreover, can be carried out without removing the upper cover 3. The same thing also takes place for the fixed sealing rings 10, 11 connected to the side covers 6, 7, balancing the wearing thereof in the case where errors in treatment or in assembly give anomalous and/or angularly unbalanced wear.
All of the wearable parts, like bearings, rings, disks and seals, are assembled on the side covers. In cases of serious breakdown, seizure, overheating and so on, which irremediably damage their seats, the pump body and the upper cover are saved. One only has to replace just the cap or the side covers which are damaged with new covers with a cost effective and simple intervention. The pump body requires much simpler treatments than pumps of the prior art; in substance, they are limited to a boring of the axis line without internal abutments and displacement of the piece on the machine tool, working only from one side. The two wide openings of the pump body 2 in correspondence with the covers 6, 7 allow, during the course of melting, better support of the cores thus realising better jets and with less waste.
Apart from in the case in which it is foreseen to be used with abrasive liquids, the pump according to the invention does not require rolling bearings. Equally, there is no need for outer lubrication devices, since all of the stresses are borne with sliding bearings and wear rings inside the pump, which are fluxed and lubricated by the pumped liquid.
In the embodiment of figure 3, the lubricating and fluxing liquid is drawn from the intake side of the pump and not from its discharge, as happens in some conventional pumps. In this way the flow system is substantially simplified, because there is no need for partialisation valves to reduce the pressure of the flow fed into the chamber 34 of the bearings and into the mechanical seal.

Claims

Centrifugal pump comprising a pump body or casing (2), a rotor (5) connected to a shaft (4), a removable upper cover (3), with the seal between the pump body (2) and the rotor (5) being taken care of by rings (10, 11) fixedly attached to the casing (2), facing rings (25), fixedly attached to the rotor (5), which are made to rotate with it characterised in that both the fixed sealing rings (10, 11) and the support bearings of the rotating part of the pump (8, 9, 8bis, 9bis) are assembled on two removable side covers (6, 7) arranged on the two sides of the pump body (2).
Centrifugal pump according to claim 1, characterised in that the support bearings of the rotating part of the pump are sliding bearings (8, 9).
Centrifugal pump according to claim 1, characterised in that the support bearings of the rotating part of the pump are lubricated rolling bearings (8bis, 9bis).
Centrifugal pump according to claim 1, characterised in that the rotor (5) is fitted onto a shaft (4) through a grooved profile (20), or alternatively with a key, which does not restrict in the axial direction.
Centrifugal pump according to claim 1, characterised in that the axial division between body (2) and upper cover (3) of the pump is realised according to a plane (13) displaced upwards and parallel to the axis line (12).
Centrifugal pump according to claim 1, characterised in that means for adjusting the clearances (22) between the sealing rings (10, 11, 25) consist of a plurality of closening screws (14, 19) and separation screws (14bis, 19bis), for the right (7) and left (6) cover, respectively, which are shaped in their outer face with a frustum of cone surface upon which the ends of the closening screws (14, 19) push in a radial direction, whereas the separation screws (14bis, 19bis) are arranged in an axial direction to pull the two covers (6, 7) outwards, such a push and pull respectively translating into an axial displacement of the covers (6, 7) inwards which draws in, or outwards which separates, the front rings (10, 11, 25) and adjusts their clearance (22).
Centrifugal pump according to claim 1, characterised in that it comprises a mechanical seal system assembled on a cover (18), smaller than and concentric with the cover (7), which carries inside of it a sealing ring (41) and a compressed spring (42) which rests on one side against the inner face of the ring (41) and on the other side against a shoulder of the shaft (4), whereas on the other side the push of the spring (42) is counteracted with a counter push by the cover (6) which compresses said spring (42) and ensures the seal.
Centrifugal pump according to claim 2, characterised in that it comprises a fluxing system of the bearings (8, 9) and of a mechanical seal (18, 41, 42) drawing fluid from the pump intake, said fluxing system being realised on the sides of the side covers (6, 7) with holes (31), which put the intake space upstream of the rotor (5) in communication with the chambers (34) next to the bearings (8, 9), and with fluxing channels (32) of the bearings (8, 9) which come out between the shoulders of said bearings and their distance rings (23, 24).
Centrifugal pump according to claim 7, characterised in that the member which controls the possible axial sliding of the shaft (4) and for applying the counter push compressing the spring (42) comprises a small cover (27), concentric with the cover (6) and fixed to it with screws, equipped inside with a sealing disk (26) which locks the axial sliding of the shaft (4).
Centrifugal pump according to claim 1, characterised in that said rotor (5) is not locked axially on the shaft and in that its axial sliding is contained by said rings (10, 11).
Centrifugal pump according to claim 3, characterised in that the lubricated rolling bearings (8bis, 9bis), which support the rotating part of the pump, are assembled outside of the two parts of the casing (2) on two support boxes (6bis, 7bis) on the side covers (6, 7).