Self aligning magnet pump

Abstract: A magnet pump with bidirectional axial self-alignment comprises an inner chamber (12) provided with a suction duct (13) and a delivery duct (14); an impeller (25) located in said chamber (12) in a rotatably and axially movable manner, and having a front portion (26) oriented towards the suction duct (13); a driven rotor (31) integral with the motor spindle (51), located outside said chamber (12) and bearing magnets (34) cooperating with as many driven magnets (35) facing the same, located in the rear portion (27) of impeller (25), and a magnet (41) fixed in the inside of said chamber (12) and cooperating with a second magnet (42), incorporated in said impeller (25) so as to realize a linear magnetic coupling.

Description: Background of the invention The present invention relates to a magnet pump with bidirectional axial self-alignment. More particularly, the present invention relates to a magnetic entraining pump suitable to support and counterbalance axial thrusts in both directions and to keep the impeller in the exact position even in extreme or abnormal operating conditions. Magnet pumps are commercially well known and described in the literature, such as for instance the British patent no. 1,134,228. They are centrifugal one-step pumps with a preferably closed impeller and are employed in liquid pumping, including chemical and corrosive ones, in water purification and recovery, heat exchangers, sea water desalination plants, etc. They include an inner chamber having a suction duct that extends axially and a delivery duct that extends circumferentially; a impeller located in the inside of said chamber so as to be in condition of rotating and possibly translating axially, said impeller having a front side oriented towards the suction duct and a rear side oriented in the opposite direction; a driving rotor located outside said chamber, fixed to a motor spindle and provided with driving magnets; a driven rotor fixed to said impeller and provided with driven magnets that face onto, and form a magnet coupling with, the driving magnets, and thrust-bearing front and rear bushes, located between the walls of the chamber and the front respectively rear side of the impeller. During the operation, the pump sucks the fluid to be transferred from the suction duct and drives it towards the delivery duct through the action of the impeller. During this action, a depression creates on the front side of the impeller that faces onto the suction duct; while the impeller and the driven rotor receive a thrust in the direction towards the suction ducts. These actions create on the impeller a thrust oriented towards the suction duct, said thrust being contrasted by the front thrust-bearing bush. In particular pressure conditions, the impeller may also translate in the opposite direction, causing the impeller guide bush to get in touch with the rear thrust-bearing bush. The pumped liquid performs also the function of dissipation of the heat that generates due to the friction between the impeller and the thrust-bearing bushes, as well as the function of lubricating said bushes, ensuring thereby the correct operation and the duration in the time. In critical or abnormal operating situations, for instance in the absence also provisional of liquid, because of vibration phenomena and the presence of gas bubbles in the sucked fluid or other causes, there lacks the axial thrust on the impeller and the friction heat dissipation and lubrication functions performed by the pumped liquid. In such conditions, as the impeller cannot be maintained any longer in its operating position abutting the front thrust-bearing bush, it may translate along the supporting spindle and get in touch with the rear thrust-bearing bush with ensuing generation of friction heat. The so developed heat that cannot be dissipated any longer may lead to severe damages of the pump and even to its seizure with ensuing working interruption. Besides, this type of pump cannot function idly, i.e. in the absence of circulating fluid, for long periods, as it would undergo severe damages arising from what has been said hereinabove. It is obvious that the aforementioned drawbacks are intolerable for magnetic entraining pumps, not only because they may lead to a complete standstill, but especially with regard to their utilization for the treatment of chemical fluids wherein possible operation interruptions may prove to be particularly damaging and deleterious to the point of causing risks for installations and people. Various devices have been proposed to obviate the above drawbacks, but none of them has allowed to solve the problem in a satisfactory and economical manner. So, for instance, it has been proposed to employ a structure from thermal insulating material to wind up the portion of the thrust-bearing bush concerned by friction. This solution, besides being expensive, involves also high temperatures in the contact points, as the insulating characteristics of the material prevent any diffusion of heat also for short lack periods; this may lead to the so-called thermal shock. It has been also proposed to employ thrust-bearing devices constituted by push rods with a round end or the like to contrast the axial shifting of the impeller. Also this solution is not free from drawbacks, as said devices involve in any case a sliding contact. Summary of the invention Object of this invention is to solve the above drawbacks. More particularly, object of this invention is to provide a magnetic entraining pump such as to ensure the operation in any running conditions, and to prevent the onset of heat or an increase in temperature due to friction contact also in extreme or abnormal operating conditions. Under its more general aspect, the present invention allows to achieve these and other objects, which will be apparent from the following description, by means of a magnetic entraining pump wherein the impeller is kept in stable equilibrium and its axial position is controlled and self-aligned in both directions, contrasting the axial thrusts and pressures which said impeller is subjected to, by means of a linear magnetic coupling between the impeller and the chamber wherein said impeller is located. Therefore, object of this invention is a magnetic entraining pump comprising an inner chamber, preferably cylindrical, provided with a section duct that extends axially and a delivery ducts that extends along the circumference; an impeller located in the inside of said chamber and having a front portion oriented towards the suction duct, a rear portion oriented towards the opposite direction, and a central support portion; a cup-shaped driving rotor, located outside said chamber and having at least a driving magnet; a driven magnet fixed to the impeller and that faces onto and forms a magnetic coupling with said driving magnet; a supporting spindle that extends axially in the chamber and that supports in a rotatably and axially movable manner said impeller, and possibly front and rear thrust-bearing bushes located on said spindle in correspondence of the front portion and the rear portion of the impeller, wherein both the chamber and the impeller are provided with at least a magnet and the respective magnets are mutually aligned and arranged according to the heteronymous poles so as to realize a linear magnetic coupling when the impeller is in a position of equilibrium between the two front and rear thrust-bearing bushes. Said magnets are arranged according to the heteronymous poles, i.e. the North pole of one of them concatenates with the South pole of the other one, and vice-versa, so that the poles attract mutually, realizing a linear magnetic coupling that keeps the impeller in a position of stable equilibrium. The magnetic coupling opposes any axial force or thrust that tends to alter the condition of equilibrium and perfect alignment of magnets. Therefore, any axial shifting of the impeller is hindered, as it involves the creation of an opposite return force, and the amount of such a return force increases as the maladjustment between the relative magnets increases. The thrust-bearing bushes may be of the mechanical type or, especially in the presence of very high axial thrusts, may be, at least partly, replaced by thrust-bearing bushes of the magnetic repelling type comprising magnets aligned and located in the impeller and the front and/or rear walls of the chamber according to the eponymous poles, i.e. with the North pole of one of them opposed to the North pole of the other one and vice-versa, so as to generate a repelling magnetic force. The constructive and functional characteristics of the magnetic entraining pump of the present invention shall be better understood thanks to the following description, wherein reference is made to the figures of the attached drawings that represent a preferred embodiment, solely given by way of non limiting example. Short description of drawings Figure 1 shows a schematic view of a section of the magnetic entraining pump of the present invention; Figure 2 shows the enlarged schematic view of detail A of Figure 1, showing the position of magnets for the realization of the linear magnetic coupling; Figure 3 shows the schematic enlarged view of a section of the pump of Figure 1 according to direction II-II; Figure 4 shows the same schematic enlarged view of Figure 3 relating to a first modification of the magnets for the magnetic coupling of Figure 1; Figure 5 shows the same schematic enlarged view of Figure 3 relating to a second modification-of the magnets for the magnetic coupling; Figure 6 shows the enlarged schematic view of detail B of Figure 1 showing a first positioning solution for the thrust-bearing bushes of the magnetic repulsion type; and Figure 7 shows the enlarged schematic view of detail C of Figure 1 showing a second positioning solution for the thrust-bearing bushes of the magnetic repulsion type. Detailed description of some preferred embodiments of the magnet pump of the present invention Figure 1 shows the magnetic entraining pump of the present invention, indicated as a whole by 10, coupled to a motor, indicated as a whole by 50. Pump 10 comprises a substantially cylindrical front portion 11, which defines a part of the inner chamber 12 and is provided with a suction duct 13 which extends in the axial direction along the axis X-X, and a delivery duct 14, which extends along its circumference. The frontal portion 11 at the rear end of suction duct 13 is provided with a conveyor 15 at whose rear end a cylindrical seat 16 is obtained suitable to house a front thrust-bearing bush 18. A substantially cylindrical rear body 20 is coupled and fixed to said front body 11, completing thereby said inner chamber 12. A sealing "O ring" is interposed between the front I 1 and rear 20 bodies to ensure the sealing of the inner chamber 12. From the bottom wall 21 of the rear body 20, in correspondence of axis X-X of the pump, a substantially cylindrical protrusion 22 extends, provided with a seat suitable to house a rear thrust-bearing bush 24. Between the front 18 and rear 24 bushes a supporting spindle 17 extends. By 25 there is indicated the impeller located in the inside of chamber 12, said impeller being supported in a rotatably and axially mobile manner by spindle 17 through front 29 and rear 30 guide bushes. Said impeller is constituted by an operating front portion 26, oriented towards the suction duct 13, a substantially cylindrical rear entraining portion 27, and a central portion 28. By 31 there is indicated a cup-shaped driving rotor located in the inside of chamber 12 and comprising a first substantially cylindrical wall 32 which embraces the rear portion of chamber 12 and a bottom wall 33 from which a substantially cylindrical portion extends that is coupled to a motor spindle 51 of motor 50. Magnets 34 are incorporated in the cylindrical portion of said driving rotor 31 and corresponding magnets 35 are incorporated in the rear portion 27 of impeller 25. Said magnets 34 and 35 are aligned with each other and located according to the heteronymous poles (North-South and South-North), and constitute an entraining magnetic couple. A stator element 40 is fixed on the inner surface of chamber 12 substantially in correspondence of the connection zone between the two front 11 and rear 20 bodies. A magnet 41 is incorporated in the stator element 40, and correspondingly, a further magnet 42 is incorporated in the central supporting portion 28 of impeller 25. Both magnets 41 and 42 are mutually aligned and placed according to the heteronymous poles forming a closed magnetic circuit, realizing thereby a linear magnetic coupling. If there have been indicated by N1 and S1 the North pole and the South pole of one, 41, of magnets, and by N2 and S2 there are indicated the North pole and the South pole of the other magnet 42, the North pole N1 of magnet 41 concatenates with the South pole S2 of magnet 42 and consequently the South S1 one of magnet 41 with the North one N2 of magnet 42. In this manner, the poles attract mutually, realizing the linear magnetic coupling, keeping the impeller in its initial equilibrium position between the two front 18 and rear 24 thrust-bearing bushes, and annulling possible axial thrusts or pressures that tend to shift the impeller from its equilibrium position. Any shifting of impeller 25 from its equilibrium position with the aligned magnets 41 and 42, generates a return magnetic force, and such force increases with the increase of shifting. Figure 3 shows the toroidal ring conformation of magnets 41 and 42. Figure 4 shows another embodiment of the magnets. Magnet 41 fixed to stator element 40 is formed by two circle arcs 41' and 41", incorporated in said stator element 40 integral with the wall of chamber 12; both magnets preferably have a quadrangular cross-section. Figure 5 shows a further embodiment of magnets 41 and 42. Magnets 41 and 42 are shaped as sectors designated by 41a, 41b, 41c, 41d, 41e, etc. and respectively 42a, 42b, 42c, etc., incorporated in the stator element 40 respectively the central support portion 28 of impeller 25. In addition or as an alternative to the thrust-bearing bushes 18 and 24 there may be employed thrust-bearing bushes of the magnetic repelling type. This type of bushes is particularly advantageous and preferred for high capacity pumps or in the presence of high axial thrusts or pressures. They comprise two magnets 43 and 44 facing each other and arranged according to the eponymous poles (North-North or South-South. The North pole 43N of one, 43 of said magnet faces the North pole 44N of the other magnet 44 or, alternatively, the South pole of the first magnet 43 faces the South pole 44S of the second magnet 44. One, 43, of the magnets may be incorporated in the front 18 and/or rear 24 thrust-bearing bush, and the other magnet 44 in the front 29 and/or rear 30 guide bush of impeller 25, as shown in Figure 6. Alternatively, magnets 43 and 44 may be used to replace at least one of the front 18 and/or rear 24 thrust-bearing bushes. Alternatively or additionally, further magnets 43' and 44', always arranged according to the eponymous poles (North pole 43'N of a magnet 43' facing the North pole 44'N of the other magnet 44') may be incorporated in the wall of the front body 11 and the front operating portion 26 of impeller 25. The arrangement according to the eponymous poles of magnets 43 and 44, and 43' and 44' generates a repelling force when the magnets are approached to each other; and such force pushes the impeller in its equilibrium position between the front 18 and rear 24 thrust-bearing bushes. In the normal running with circulating fluid, the electric motor 50 causes driving rotor 31 to rotate and keeps it rotating though spindle 51, which rotor, in its turn, cause impeller 25 to rotate and keeps it rotating through the magnetic coupling that exists between magnets 34 and 35. With its rotation, impeller 25 conveys by centrifugal action the fluid to be transferred through chamber 12 towards the delivery duct 14, piping it from the delivery duct 13. The pressure difference that exists between chamber 12 and suction duct 13 generates an axial thrust that keeps impeller 25 abutting, with the front surface of guide bush 29, onto the front thrust-bearing bush 18. Impeller 25 may also translate in the opposite direction in special pressure conditions, bringing guide bush 30 in touch with the rear thrust-bearing bush 24. Such axial shifts of the impeller are contrasted by the return magnetic force of magnets 41 and 42. In case of particular phenomena, such as vibrations or gas bubbles in the treated fluid, there lacks the axial thrust that keeps impeller 25 in its normal operating condition, and in this situation impeller 25 is caused to return towards the central equilibrium position, realigning magnets 41 and 42 and eliminating any contacts between the rotary guide bushes 29 and 30 and the front 18 and rear 19 thrust-bearing bushes. From the above description, the advantages which the bidirectional axially self-aligning magnet pump of the present invention allows to achieve are evident. It eliminates and prevents the sliding contacts in the axial direction of the impeller on the trust-bearing bushes, as the magnetic couple opposes any axial shift of the impeller with respect to its equilibrium position. Any axial shift of the impelled is prevented since its onset and the return force increase as the misalignment between the magnets. Thanks to these characteristics the magnetic traction pump of the present invention may work even without the presence of fluids, and supports without any damages abnormal and critical conditions as those described. Besides, the magnetic traction pump of the present invention is particularly simple from the point of view of construction and may be produced to contained realization costs, and thanks to its working characteristics may be employed in many applications with very different requirements and assures the operation in any situations, also abnormal, that may occur. While this invention has been described with reference to a preferred realization embodiment, solely given by way of illustration and example, various changes and variants will be obvious for those skilled in the art, in the light of the above description. Therefore, the present invention intends to comprise all the changes and variants that fall within the protection scope of the appended claims.

Claims: A magnet pump with bidirectional axial self-alignment comprising a preferably cylindrical inner chamber (12) provided with a suction duct (13) that extends axially and a delivery duct (14) that extends along the circumference; an impeller (25) located in the inside of said chamber (12) and having a front portion (26) facing the suction duct (13), a rear portion (27) facing the opposite direction, and a central support portion (28); a cup-shaped driving rotor (31) located outside said chamber (12) and having at least a driving magnet (34); a driven magnet (35) incorporated in said impeller (25) and that faces on and form a magnetic coupling with said driving magnet (34); a supporting spindle (17) that extends axially in said chamber (12) and that supports in a rotatably and axially movable manner said impeller (25); and possibly front (18) and rear (24) thrust-bearing bushes located on said spindle, in correspondence of the front portion (26) and the rear portion (27) of said impeller (25), characterized in that said impeller (25) is kept in stable equilibrium and its axial position is maintained controlled and self-aligned in both directions by means of a linear magnetic coupling between said impeller (25) and said chamber (12) wherein said impeller is located. The magnet pump according to claim 1, wherein the magnetic coupling is realized by means of two magnets (41, 42) incorporated in the wall of chamber (12) respectively the central portion (28) of impeller (25), said magnets (41, 42) being mutually aligned and arranged according to the heteronymous poles (North-South and South-North) in such a way as to realize a closed magnetic circuit. The magnet pump according to claim 1 or 2, wherein chamber (12) is formed by a front body (11) and a rear body (20) sealed with each other, and its internal surface, in correspondence of the connection zone between the two bodies (11, 20) is provided with a stator element (40) wherein there is incorporate one (41) of the magnets for the linear magnetic coupling. The magnet pump according to any of the preceding claims, wherein magnets (41, 42) are shaped as toroidal rings. The magnet pump according to any of the preceding claims 1-3, wherein at least one of the magnets (41, 42) is shaped as an arc of circle (41', 41"). The magnet pump according to any of the preceding claims 1-3, wherein at least one of the magnets (41, 42) is shaped as a sector (41a, 41b, 41c, 41d, etc., and 42a, 42b, 42c, etc.). The magnet pump according to any of the preceding claims, wherein at least one of the thrust-bearing bushes (18, 24) is of a magnetic repelling type and comprises two magnets (43, 44), facing each other and arranged according to the eponymous poles (North-North or South-South). The magnet pump according to claim 7, wherein a magnet (43) is incorporated in the thrust-bearing bush (18, 24) and the other magnet is incorporated in the guide bush (29, 30) of the impeller. The magnet pump according to any of the preceding claims, characterized in that it comprises at least a further magnetic repelling thrust-bearing bush comprising two magnets (43', 44'), facing each other and arranged according to the eponymous poles (North-North or South-South), one of which (43') is incorporated in the wall of the front body (11) and the other one (44') in the operating front portion of impeller (25).

Inventors: GABRIELI OMAR, GENNARI FRANCESCO, GABRIELI, OMAR, GENNARI, FRANCESCO
Applicants: ARGAL S R L, ARGAL S.R.L.
Application year: 2000
Main classification: F04D13
IPC codes: F04D13