Technical field of the invention
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The present invention relates generally to the field of centrifugal pumps, for instance heating circulation pumps. The present invention relates specifically to a sealing arrangement suitable for said pumps and applications, i.e. a pump comprising such a sealing arrangement.
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The present invention relates to a centrifugal pump comprising a drive unit having an electric motor and a drive shaft, wherein the drive shaft extends in an axial direction. The centrifugal pump further comprises a hydraulic unit connected to the drive unit, wherein the hydraulic unit comprises an inlet and an outlet, a housing defining a volute, and an impeller connected to the drive shaft and located in said volute. The impeller comprises a lower cover disc, an upper cover disc and at least one vane extending between and connecting said lower cover disc and said upper cover disc. The hydraulic unit further comprises a sealing arrangement connected to the housing and configured for sealing between an inlet of the lower cover disc of the impeller and the housing, wherein the sealing arrangement comprises a circumferential seal member and a clamping member.
Background of the invention
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In several industrial applications, such as in mines, tunneling, quarries, on construction sites, and the like applications, there is almost always a need to transport fluid or to remove unwanted water in order to secure a dry enough environment at the working site. Other applications also having more or less continuous operation are heating circulation pumps. A known efficient alternative is the utilization of centrifugal pumps in order to remove and transfer fluids in such applications/situations. A centrifugal pump is a mechanical device designed to move a fluid by means of the transfer of rotational energy from one or more impellers. When the fluid enters the rotating impeller, the fluid is caught in the vane structure of the impeller and is transported radially/ transversally outwards by the centrifugal force caused by the rotation of the impeller. The action of the impeller increases the velocity and pressure of the fluid.
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A centrifugal pump comprises a rotating part comprising the impeller and a stationary part surrounding the rotating impeller. Between the stationary part and the rotating impeller there are gaps. The gaps must be efficiently sealed both to avoid fluid leakage between the gaps, as well as to maintain the pressure inside the fluidic system.
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Sealing arrangements, also called wear rings, may be used to provide a seal-like construction to seal the interface between a rotating impeller and a stationary part of a centrifugal pump. Sealing arrangements usually comprise a stationary part and a seal member attached to the stationary part. The seal member is provided between the stationary part of the sealing arrangement and the rotating impeller. It is important that the seal member is configured in such a manner not to negatively interfere with the rotational movement of the impeller while at the same time functioning as an efficient seal. According to known solutions, the seal member may either be rotationally fixed in relation to the rotating impeller, or allowed to freely rotate together with the impeller.
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However, as the rotating impeller may experience small shifts in radial/transversal position during operation, contact/impact between the impeller and the seal member may occur. Such contact results in high forces, leading to damage of the sealing member and the impeller, as well as noise and vibrations. Moreover, in a seal member rotationally fixed in relation to the rotating impeller, contact may also lead to the seal member starting to rotate in the rotational direction of the impeller, which may cause great damage to the seal member due to wear of the rotating seal member in relation the stationary part.
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The prior art proposes solutions where some degree of movement of the seal member in the transversal/radial direction in relation to the rotating impeller is allowed. For instance, the sealing arrangement may be constructed in such a way to allow some degree of movement in the radial and axial direction of the seal member relative the rotating impeller. However, in seal members rotationally fixed in relation to the rotating impeller, rotational movement of the seal member is undesired. A known solution is for instance disclosed in
US8721263 , disclosing a seal member exhibiting no rotational movement of the seal member in relation to the rotating impeller.
JP 2018115597 discloses a seal member of a pump, wherein the seal member is located between two ring elements that are jointly attached to the housing of the pump. The seal member is not clamped between the two ring elements but will float/move uncontrollably in the radial/transversal direction during operation of the pump.
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If the seal member would start to rotate together with the rotating impeller, this may lead to increased mechanical forces at contact points between the seal member and the rotating impeller, as well as between the seal member and the stationary part of the wear ring.
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As such, uncontrolled radial and/or rotational movement of the seal member is unwanted as it may result in increased wear of components, as well as noise and vibrations. A proposed solution to avoid rotational movement of the seal member has been to decrease the efficiency of the centrifugal pump so to reduce the forces acting on the seal member in case of mechanical contact.
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Thus, there is a need to be able to obtain a centrifugal pump comprising a sealing arrangement having improved wear characteristic without the need to reduce efficiency of the centrifugal pump.
Object of the invention
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The present invention aims at obviating the aforementioned disadvantages and failings of previously known centrifugal pumps, more specifically sealing arrangements for centrifugal pumps. A primary object of the present invention is to provide an improved centrifugal pump of the initially defined type that comprises a sealing arrangement achieving reduced wear, and thereby improved efficiency as well as reduced noise.
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It is another object of the invention to provide an improved centrifugal pump comprising a sealing arrangement that reduces the risk of noise during operating of the centrifugal pump.
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It is another object of the present invention to provide an improved centrifugal pump comprising a sealing arrangement allowing for easy assembly and low material cost.
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It is another object of the present invention to provide an improved centrifugal pump comprising a sealing arrangement preventing backflow from the outlet side of the pump to the inlet side of the pump, i.e. prevent hydraulic losses.
Summary of the invention
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According to the invention at least the primary object is attained by means of the initially defined centrifugal pump comprising a sealing arrangement having the features defined in the independent claims. Preferred embodiments of the present invention are further defined in the dependent claims.
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According to the present invention, the seal member is clamped in the axial direction between the clamping member and the housing, wherein the seal member is displaceable in the radial direction in relation to the clamping member, wherein the seal member comprises a first engagement means and the clamping member comprises a second engagement means configured to cooperate with the first engagement means of the seal member. The sealing arrangement has a play in the circumferential direction between the first engagement means and the second engagement means whereby the seal member is displaceable in the rotational direction in relation to the clamping member at an angle α that is equal to or less than ± 3 degrees, and whereby the seal member is displaceable in the circumferential direction in relation to the clamping member an angle α that is equal to or more than ± 0.3 degrees.
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Thus, the invention is based on the insight that by providing a sealing arrangement having a seal member displaceable in a controlled way in the radial/transversal direction in relation to the clamping member, as well as having a play in the circumferential/rotational direction in relation to the clamping member at an angle that is equal to or less than ± 3 degrees in relation to a nominal position and equal to or more than ± 0.3 degrees, it is possible to achieve an improved and limited floating ability of the seal member within the volute. By limited floating ability, it is meant the ability of the seal member to move/deflect in the radial direction and in the circumferential direction in response to mechanical contact with the impeller. The displaceability in the radial direction and in the circumferential direction is damped/restricted by means of frictional forces between the clamping member and the seal member, since the seal member is clamped in the axial direction between the clamping member and the housing. It has surprisingly been discovered that by allowing the seal member to have a controlled play in the circumferential direction according to the present invention, the efficiency of the centrifugal pump can be increased. This is due to the configuration of the sealing arrangement that, if mechanical contact between the rotating impeller and the seal member occurs, allows the seal member to displace both in the radial direction and to a small extent also in the circumferential direction in relation to the clamping member. By allowing the seal member to have a controlled displacement in the radial direction as well as a controlled displacement in the circumferential direction, the mechanical forces arising from the contact/impact between the rotating impeller and the seal member can better be absorbed and distributed between the components, thus decreasing wear and damage of the seal member and of the impeller. The play in the circumferential direction is however kept at low angular values as full rotation of the seal member is undesired as previously described. As a result, the sealing arrangement according to the present invention wear at a much lower rate than a fixed non-floating sealing arrangement, and also at a lower rate compared to sealing arrangements only displaceable in the transversal/radial direction. Moreover, by improving the limited floating ability of the seal member, noise resulting from mechanical contact is also decreased, thus improving working environment.
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According to various embodiments of the present invention, the seal member is displaceable in the rotational direction in relation to the clamping member an angle α that is equal to or less than ± 1,5 degrees. Thereby, an even more reduced wear of wear and damage of the seal member and the impeller is achieved.
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According to various embodiments of the present invention, the clamping member is ring-shaped, and is in press fit connection with the housing. Thereby, the clamping member provides a fixed engagement point for the seal member.
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According to various embodiments of the present invention, the seal member comprises an inner seal ring and an outer seal ring connected to each other, wherein the inlet of the lower cover disc of the impeller is located between the inner seal ring and the outer seal ring of the seal member. Thereby, the radial displaceability of the seal member in relation to the clamping member is further improved at the same time as efficient sealing is achieved.
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According to various embodiments of the present invention, the seal member comprises a flange connected to and extending from the outer seal ring outwards in the radial direction, wherein the clamping member clamp said flange in the axial direction. Thereby, the degree of displaceability of the seal member in the axial direction in relation to the clamping member is limited, and the clamping member provides a friction/resistance to displacement of the seal member.
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According to various embodiments of the present invention, the seal member is made of rubber or plastic.
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According to various embodiments of the present invention, the clamping member is made of metal.
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According to various embodiments of the present invention, the centrifugal pump is constituted by a heating circulation pump.
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Further advantages with the features of the invention will be apparent from the following detailed description of preferred embodiments.
Brief description of the drawings
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A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein:
- Fig. 1
- is a schematic cross-sectional side view of an inventive centrifugal pump comprising an inventive sealing arrangement,
- Fig. 2
- is a schematic view from above of a sealing arrangement comprising a circumferential seal member and a clamping member,
- Fig. 3
- is a schematic enlarged view from above of a part of the sealing arrangement according to Figure 2, and
- Fig. 4
- is a schematic cross-sectional view of a sealing arrangement and an impeller together with the stationary part of the centrifugal pump.
Detailed description of preferred embodiments of the invention
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The present invention relates specifically to the field of centrifugal pumps, for instance heating circulation pumps. The present invention relates specifically to a sealing arrangement suitable for such centrifugal pumps and such applications, i.e. to a centrifugal pump comprising such a sealing arrangement, wherein the sealing arrangement is configured to reduce noise/vibrations and to prevent flow-losses due to backflow of water from the outlet side to the inlet side of the impeller of the pump.
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Reference is initially made to Figure 1, disclosing a schematic illustration of a cross-sectional side view of a centrifugal pump, generally designated 1. The general structure elements of a centrifugal pump 1 will be described with reference to Figure 1. The centrifugal pump 1 comprises a drive unit, generally designated 2. The drive unit 2 of the centrifugal pump 1 comprises an electric motor, generally designated 3, and a drive shaft 4 extending from the electric motor 3 in an axial direction. The centrifugal pump 1 further comprises a hydraulic unit, generally designated 5, connected to the drive unit 2.
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The hydraulic unit 5 of the centrifugal pump 1 comprises an inlet 6, an outlet 7 and a housing 8 defining a volute 9. The volute 9 is located downstream the inlet 6 and upstream the outlet 7. An impeller 10, connected to the drive shaft 4, is located within the volute 9.
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The impeller 10 is connected to and driven in rotation by the drive shaft 4 during operation of the centrifugal pump 1. The impeller 10 comprises a lower cover disc 11, an upper cover disc 12 and at least one vane extending between and connecting said lower cover disc 11 and said upper cover disc 12. When the impeller 10 is driven in rotation by the drive shaft 4, liquid is sucked into said inlet 6 and pumped out through said outlet 7 by means of the rotating impeller 10 when the centrifugal pump 1 is active. In Figure 1, the inlet 6 is configured such that the liquid to be pumped enters the volute 9 in essentially the axial direction and exits the volute in essentially a transversal/radial direction from the outlet 7.
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The housing 8 and the impeller 10 are preferably made of metal, such as aluminum and steel. The electric motor 3 may be powered via an electric power cable (not illustrated) extending from a power supply.
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The centrifugal pump 1 further comprises a sealing arrangement 13, 14 connected to the housing 8. The sealing arrangement 13, 14 is arranged for sealing a gap formed between the lower cover disc 11 of the impeller 10 and the housing 8, i.e. to prevent backflow from the outlet side of the pump to the inlet side of the pump. According to the disclosed embodiment, the sealing arrangement 13, 14 is constituted by solely two components, i.e. the sealing arrangement comprises a circumferential seal member 13 and a clamping member 14. The clamping member 14 is configured to retain/clamp the circumferential seal member 13 in the axial direction between the clamping member 14 and the housing 8.
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According to various embodiments of the present invention, the centrifugal pump 1 is constituted by a heating circulation pump.
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Reference is now made to Figures 2-3, disclosing the inventive sealing arrangement 13, 14 in more detail. The present invention is based on a new improved sealing arrangement 13, 14, that is configured to be used in centrifugal pumps 1. The sealing arrangement 13, 14 is configured in such a way that the seal member 13 is allowed a certain degree of freedom in the transversal/radial direction, and to some extent also in the circumferential/rotational direction as will be described more below. The radial direction is considered in relation to the clamping member 14, that is fixed to the housing 8, and in relation to the housing 8. The circumferential direction is considered in relation to the clamping member 14, that is fixed to the housing 8, and in relation to the housing 8.
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Figure 2 discloses a schematic view from above of the sealing arrangement 13, 14 comprising the circumferential seal member 13 and the ring-shaped clamping member 14. As can be seen in Figure 2, the circumferential seal member 13 is mainly located within the ring-shaped clamping member 14 and overlap an internal circumference of the ring-shaped clamping member 14. The seal member 13 may be engaged with the ring-shaped clamping member 14 by any suitable engagement means configured to cooperate with corresponding engagement means arranged on the ring-shaped clamping member 14. The engagement means are configured in such a way that the seal member 13 is displaceable, i.e. movable, in the radial direction in relation to the ring-shaped clamping member 14. Moreover, the engagement means are further configured to allow the seal member 13 a play, i.e. a controlled degree of movement, in the circumferential direction in relation to the clamping member 14. According to the present invention, it has been found that by allowing a rotational play in an angle α that is equal or less than ± 3 degrees in relation to a nominal position, preferably equal to or less than ± 1,5 degrees, the wear of the sealing arrangement 13, 14 can be significantly reduced. The expression, ± 3 degrees, means 3 degrees in each direction in relation to a nominal position. The ability of the seal member 13 to be displaceable not only in the radial direction in relation to the ring-shaped clamping member 14, but also in the circumferential direction with a controlled play equal to or less than ± 3 degrees allows for improved force distribution if contact/impact between the seal member 13 and the rotation impeller 10 occurs. However, the rotational play of the seal member 13 is kept at a low angular value, as excessive angular movement would cause wear and damage to the seal member 13.
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Further, the seal member 13 is displaceable in the rotational direction in relation to the ring-shaped clamping member 14 in an angle α that is equal or more than ± 0.3 degrees. Thus, the seal member 13 is always given a minimum degree of movement/displaceability in the circumferential direction in relation to the clamping member 14 also when the seal member 13 is displaced in the radial/transversal direction in relation to the clamping member 14.
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According to various embodiments, the seal member 13 is made of rubber or plastic. Rubber or plastics are advantageous as they are resilient and flexible materials allowing for a degree of displacement, a degree of elastic deformation, as well as being wear resistant.
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According to various embodiments, the clamping member 14 is made of metal, such as aluminum and steel.
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Reference is now made to Figure 3, disclosing a schematic enlarged cross-sectional view of the sealing arrangement 13, 14 in cooperation with the impeller 10. Figure 3 illustrates engagement means 15, 16 according to various embodiments of the present invention, allowing the seal member to be displaceable in the radial direction in relation to the clamping member 14, as well as having a play in the circumferential/rotational direction in relation to the ring-shaped clamping member 14 according to the present invention.
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As can be seen in Figure 3, the circumferential seal member 13 comprises, located on an outer circumferential side, a first engagement means 15. The ring-shaped clamping member 14 comprises a second engagement means 16. The second engagement means 16 of the ring-shaped clamping member 14 is configured to cooperate with the first engagement means 15 of the circumferential seal member 13.
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According to various embodiments, as illustrated in Figure 3, the first engagement means 15 of the circumferential seal member 13 is constituted by at least one projection 15 extending in the radial direction. According to various embodiments, as illustrated in Figure 3, the second engagement means 16 of the ring-shaped clamping member 14 is constituted by at least one recess 16 extending in the radial direction. In such embodiments, the projection 15 extends radially into the recess 16, thus forming an engagement means keeping the circumferential seal member 13 in position. The engagement means 15, 16 are configured so that the seal member may be displaced in the radial direction in relation to the ring-shaped clamping member 14. Also, the engagement means are configured so that a controlled rotational play of the circumferential seal member 13, in relation to the ring-shaped clamping member 14, at an angle that is equal to or less than ± 3 degrees is possible, and equal to or more than ± 0,3 degrees. This provides the sealing arrangement 13, 14 with the restricted floating abilities in both the radial direction and the circumferential direction as previously described.
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Reference is now made to Figure 4, disclosing a schematic cross-sectional view of an inventive sealing arrangement and an impeller 10 together with the stationary part of the centrifugal pump.
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As previously described under Figure 1, during operation of the centrifugal pump, pumpable liquid enters the hydraulic unit 5 of the centrifugal pump through the inlet 6 and into the volute 9. The rotatable impeller 10, as previously described under Figure 1, is located within the volute 9, and connected to the drive shaft 4.
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The impeller 10 disclosed in Figure 4 comprises a lower cover disc 11 and upper cover disc 12. The volume between said lower cover disc 11 and the upper cover disc 12 defines a vane extending between and connecting the two discs 11, 12. When the impeller 10 rotates, liquid is sucked into the impeller 10 and forced out of the impeller 10 by way of centrifugal force. The diameter of the impeller 10 and the shape and configuration of the vanes determines the pressure build up in the liquid and the pumped flow.
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According to the invention, the hydraulic unit 5 further comprises the sealing arrangement 13, 14. In the embodiment disclosed in Figure 4, the sealing arrangement comprises the circumferential seal member 13 and the ring-shaped clamping member 14 as previously described. The sealing arrangement is located towards the inlet 6 of the centrifugal pump and seals a gap formed between the housing 8 and the inlet of the impeller 10.
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According to various embodiments of the invention, during operation of the centrifugal pump 1, the seal member 13 may come in contact with the inlet of the lower cover disc 11 of the impeller 10 due to bending of the drive shaft 4, forcing the seal member 13 to a displacement in the radial direction in relation to the clamping member 14. Hence, the seal member 13 is allowed a degree of movement in the radial direction to accommodate for any positional variations of the impeller 10 in the radial direction due to bending of the drive shaft 4 during operation of the centrifugal pump. This results in reduced wear of the sealing member 13 and the impeller 10.
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According to various embodiments of the invention, as illustrated in Figure 4, the circular clamping member 14 is in press-fit connection with the housing 8. The clamping member 14 is thus fixedly connectable to the housing 8 and does not move in relation to the impeller 10 during operation of the centrifugal pump 1. The circular clamping member 14 functions as a holder for the circumferential seal member 13, that is arranged within the ring-shaped clamping member 14 and clamped between the clamping member 14 and the housing 8. The seal member 13 is however, contrary to the clamping member 14, displaceable in the radial direction and in the rotational direction in relation to the clamping member 14 as previously described. Since the seal member 13 is clamped by the clamping member 14, there is a friction that restricts the movement of the seal member 13 in the radial/transversal direction in relation to the clamping member 14, which prevents vibrations and noise.
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According to various embodiments of the invention, as further illustrated in Figure 4, the seal member 13 comprises an inner seal ring 17. The seal member 13 further comprises an outer seal ring 18 connected to the inner seal ring 17. The inner seal ring 17 and the outer seal ring 18 thus defines a U-shaped space wherein an inlet 19 of the lower cover disc 11 can be located. This allows for an even more improved radial displaceability of the seal member 13 during rotation of the impeller 10, at the same time as efficient sealing is achieved. During operation of the centrifugal pump 1, the impeller 10 may not be completely aligned with the default drive shaft axis. These relative movements of the impeller 10 may result in contact between the impeller 10 and the seal member 13. By allowing the seal member 13 to be displaced in the radial direction in relation to the clamping members, the seal member 13 may work as a damper absorbing mechanical forces caused by contact between the impeller 10 and the seal member 13. The radial floating ability decreases wear of the components, as well as friction.
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According to various embodiments of the present invention, the seal member 13 comprises a flange 20. The flange 20 is connected to the outer seal ring 18. As can be seen in Figure 4, the flange 20 extends outwards from the outer seal ring 18 of the seal member 13 in a radial direction. The circular clamping member 14 clamp said flange 20 in the axial direction, thus preventing displaceability of the seal member in the axial direction and provides a friction/resistance for movement of the seal member 13 in the radial direction in relation to the clamping member 14. This further improve the dampening properties of the seal member 13 if contact between the rotating impeller 10 and the seal member 13 occurs.
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According to various embodiments of the present invention, there is a small gap in the radial/transversal direction between the inlet 19 of the lower cover disc 11 of the impeller 10 and the inner seal ring 17, and there is a small gap in the radial/transversal direction between the inlet 19 of the lower cover disc 11 of the impeller 10 and the outer seal ring 18, in order to reduce wear/friction during ordinary operation of the pump. Said gaps are preferably equal to or more than 0,25 mm and equal to or less than 0,5 mm.
Feasible modifications of the invention
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The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.
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It shall also be pointed out that all information about/concerning terms such as above, under, upper, lower, etc., shall be interpreted/read having the equipment oriented according to the figures, having the drawings oriented such that the references can be properly read. Thus, such terms only indicate mutual relations in the shown embodiments, which relations may be changed if the inventive equipment is provided with another structure/design.
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It shall also be pointed out that even thus it is not explicitly stated that features from a specific embodiment may be combined with features from another embodiment, the combination shall be considered obvious, if the combination is possible.