SHAFT SUPPORT FOR SUPPORTING AN AGITATOR SHAFT AND AN AGITATOR

Abstract

The disclosure relates to a shaft support for supporting a lower portion of a rotatable shaft of an agitator configured to be installed in a tank, the shaft support comprising a support ring with an inwardly facing bearing surface configured to form a slide bearing journaling a lower portion of the rotatable shaft, wherein the bearing surface has a non-circular shape in a plane having a normal parallel to the shaft axis.

Claims

1. A shaft support for supporting a lower portion of a rotatable shaft extending downwardly along a shaft axis from a drive arrangement, the shaft support comprising: a support ring extending around a central geometrical axis and being configured to circumscribe the lower portion of the rotatable shaft, the support ring having an inwardly facing bearing surface configured to form a slide bearing journaling the lower portion of the rotatable shaft, wherein the bearing surface has a non-circular shape, as seen in a projection in a plane having a normal parallel to the shaft axis, in the sense that a first distance, which is measured in a first direction in the plane and which forms a longest distance between the bearing surface and a circle representing an outer envelope surface of the shaft is larger than a second distance, which is measured in a second direction in the plane and which forms a shortest distance between the bearing surface and the circle representing the outer envelope surface of the shaft, wherein the second distance is less than 70% of the first distance.

2. The shaft support according to claim 1, wherein the non-circular shape of the bearing surface, as seen in the plane having a normal parallel to the shaft axis, is at least partly provided by the support ring being tilted relative to the plane having a normal parallel to the shaft axis.

3. The shaft support according to claim 1, wherein the bearing surface is formed as an ellipse as seen in a projection in the plane having a normal parallel to the shaft axis.

4. The shaft support according to claim 1, wherein the bearing surface extends circularly around the central geometrical axis of the support ring.

5. The shaft support according to 4 claim 1, wherein the bearing surface has a convex cross-sectional shape, as seen in a radial plane extending radially from the central geometrical axis of the support ring, the bearing surface having a convex shape in the sense that a central portion of the bearing surface, as seen along the central geometrical axis, of the bearing surface bulges inwardly towards the central geometrical axis.

6. The shaft support according to claim 1, wherein the support ring is made of metal.

7. The shaft support according to claim 1, wherein the bearing surface is configured to allow the lower portion of the rotatable shaft to slidably move up and down relative to the bearing surface.

8. The shaft support according to claim 1, the shaft support comprising a support structure configured to extend downwardly and to be attached to a bottom of a tank into which the rotatable shaft is intended to extend into.

9. The shaft support according to claim 8, wherein the support structure is configured to be attached centred relative to a geometrical point where the shaft axis intersects the bottom of the tank.

10. An agitator configured to be installed in a tank, the agitator comprising a drive arrangement, an agitator shaft being provided with agitator blades and being configured to extend downwardly from the drive arrangement along a shaft axis and to be rotated about the shaft axis by the drive arrangement, and a shaft support according to claim 1.

11. The agitator according to claim 10, wherein the lower portion of the agitator shaft is provided with a bushing configured to interact with the bearing surface of the shaft support.

12. The agitator according to claim 11, wherein the bushing is composed of polymer-based or ceramic-based material.

13. The agitator according to claim 11, wherein the bushing is made of a material being softer than the material forming the bearing surface.

14. The agitator according to claim 10, wherein there is a radial play between the bearing surface and the lower portion of the agitator shaft.

15. The agitator according to claim 14, wherein the bearing surface defines a smallest geometrical cylinder of free space along the shaft axis, the smallest geometrical cylinder of free space having a diameter being larger than the diameter of the lower portion of the agitator shaft.

16. The agitator according to claim 11, wherein the bushing is composed of polymer-based or ceramic-based food grade material.

17. The agitator according to claim 11, wherein there is a radial play between the bearing surface and the bushing at the lower portion of the agitator shaft.

18. The agitator according to claim 17, wherein the bearing surface defines a smallest geometrical cylinder of free space along the shaft axis, the smallest geometrical cylinder of free space having a diameter being larger than the diameter of the bushing at the lower portion of the agitator shaft.

19. The agitator according to claim 15, wherein the smallest geometrical cylinder of free space has a diameter at least 5% larger than the diameter of the lower portion of the agitator shaft.

20. The agitator according to claim 15, wherein the smallest geometrical cylinder of free space has a diameter at least 1% larger than the diameter of the lower portion of the agitator shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

[0056] FIG. 1 discloses an agitator comprising a shaft provided with agitator blades, a drive arrangement and a shaft support.

[0057] FIG. 2 is a perspective view of the shaft support of FIG. 1.

[0058] FIG. 3a is a top-plan view of the shaft support of FIGS. 1 and 2.

[0059] FIG. 3b is an enlargement of part of FIG. 3a.

[0060] FIG. 4 is side view of the shaft support of FIGS. 1-3.

[0061] FIG. 5 is a cross-sectional view of a support ring of the shaft support.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0062] In FIG. 1 there is disclosed an agitator 3 configured to be installed in a tank. The agitator 3 comprises a drive arrangement 4 and an agitator shaft 2. The agitator shaft 2 extends downwardly from the drive arrangement 4 along a shaft axis L down to a shaft support 1. The shaft axis L may also be referred to as a longitudinal direction L.

[0063] The drive arrangement 4 may e.g. be a motor, such as an electrical motor, a hydraulic motor or the like. Depending upon the working range of the motor when it comes to rotational speed and torque and the intended rotational speed and torque demand of the agitator shaft 2, the drive arrangement 4 may include a gear. The drive arrangement 4 may also comprise a clutch. The clutch may be used during start-up and shut-down. A clutch may also be used to release the connection between the motor and the agitator shaft 2 as a safety precaution, such as if the agitator shaft 2 becomes stuck.

[0064] The agitator shaft 2 is provided with a plurality of agitator blades 7. The agitator blades 7 are distributed along the shaft axis L and are provided along at least a portion of the shaft 2, from the drive arrangement 4 down towards the shaft support 1. The agitator blades 7 each extend outwardly from the agitator shaft 2. In the disclosed embodiment they extend perpendicular to the shaft axis L. In the disclosed embodiment there are four agitator blades 7 at each longitudinal position where there are provided blades. The blades are attached to a ring 17 which in turn encloses and is connected to a small portion of the agitator shaft 2. The agitator blades 7 are attached to the shaft 2 such that the blades 7 sweep around the shaft axis L when the shaft 2 is rotated by the drive arrangement 4. The actual design and configuration may be varied in a number of different ways.

[0065] As disclosed in FIG. 1, a lower portion of the rotatable shaft 2 is supported by the shaft support 1. The shaft support 1 comprises a support ring 5. The support ring 5 extends around a central geometrical axis C. The support ring 5 is configured to circumscribe the lower portion of the rotatable shaft 2. The agitator shaft 2 is configured to be inserted from the top of the support ring 5. The support ring 5 has preferably an extension along the shaft axis L and a position as seen along the shaft axis L such that the shaft 2 extends completely through the support ring 5. The support ring 5 is configured to be connected to a bottom or a wall, preferably the bottom, of the tank and be held in the intended position by a support structure 8a-c. The support structure 8a-c extends downwardly along the shaft axis L from the support ring 5.

[0066] The support ring 5 has an inwardly facing bearing surface 6 which is configured to form a slide bearing journaling the lower portion of the rotatable shaft 2. Thus, the bearing surface 6 of the shaft support 1 support a lower portion of the agitator shaft 2.

[0067] As shown in FIGS. 3a-b, the shape of the bearing surface 6 is non-circular as seen in the projection in a plane, the plane of the paper in FIGS. 3a and 3b, having a normal parallel to the shaft axis L. The shape of the bearing surface 6 may be non-circular in the sense that a first distance d.sub.1, which is measured in a first direction in the plane and which forms a longest distance between the bearing surface 6 and a circle representing an outer envelope surface of the shaft 2 is larger than a second distance d.sub.2, which is measured in a second direction in the plane and which forms a shortest distance between the bearing surface 6 and the circle representing the outer envelope surface of the shaft 2, wherein the second distance d.sub.2 is less than 70%, preferably less than 65% and more preferably less than 60% of the first distance d.sub.1. This non-circularity is provided in order to disturb the rolling effect and thereby to eliminate the vibration building up otherwise often occurring.

[0068] The available choices of the values of the second distance d.sub.2 may in such a case be described with the formula, 0<d.sub.2<Y×d.sub.1, where Y is 0.7, preferably 0.65, and more preferably 0.6.

[0069] Most preferably it has been found that the second distance d2 should be less than 56% of the distance d1 . The available choices of the values of the second distance d.sub.2 may in such a case be described with the formula, 0<d.sub.2<0.56×d.sub.1.

[0070] The first distance d.sub.1 may be said to be the longest distance between the bearing surface 6 and the circle representing the outer envelope surface of the shaft 2 and the second distance d.sub.2 may be said to be the shortest distance between the bearing surface 6 and the circle representing the outer envelope surface of the shaft 2 in the same plane.

[0071] The non-circular shape of the bearing surface 6 may at least be partly provided by the support ring 5 being tilted relative to the plane P having a normal parallel to the shaft axis L. The bearing surface 6 may be formed as an ellipse as seen in a projection in the plane having a normal parallel to the shaft axis L. The difference between the first distance d.sub.1 and the second distance d.sub.2 is dependent on how much the support ring 5 becomes tilted. A larger tilt gives a larger difference between the first and the second distance, d.sub.1 and d.sub.2. The bigger the first distance d.sub.1 is the bigger angle the support ring can be tilted. The support ring 5 may represent a bearing surface 6 having a circular shape in the plane having a normal parallel to the shaft axis L if not being tilted. Alternatively expressed, the support ring 5 may represent a bearing surface 6 having a circular shape in the plane having a normal parallel to the central axis C.

[0072] The shaft support 1 may comprise a support structure 8a-c configured to extend downwardly. The support structure 8a-c may be attached to a bottom of a tank into which the rotatable shaft 2 is intended to extend into. The support structure 8a-c may comprise rods 8a-c as can be seen in e.g. FIG. 1. Since support ring 5, in FIG. 1, has a circular shape and is tilted, the lengths of the rods 8a-c have been adjusted into different lengths to connect to the bottom of the tank. The rods 8a-c are typically designed such that each rod carries the same forces while the agitator shaft 2 is rotating. They are evenly distributed on the support ring 5 and their connection points on the bottom of the tank is evenly distributed, preferably evenly distributed on a common geometrical circle, as may be seen in FIG. 2.

[0073] The support structure 8a-c may be configured to be attached centred relative to a geometrical point where the shaft axis L intersects the bottom of the tank. In the disclosed embodiment this is provided by the common geometrical circle of the connection points of the rods 8a-c having a centre point coinciding with the geometrical point where the shaft axis L intersects the bottom of the tank

[0074] The bearing surface 6 of the shaft support 1 may extend circularly around the central geometrical axis C of the support ring 5. The distance from the central geometrical axis C of the support ring 5 to the bearing surface 6 may be equal in each point in a plane, having normal parallel to the central geometrical axis C, around the circular extension of the bearing surface 6. The radial thickness of the support ring 5 is preferably uniform as seen along the circular shape around the central geometrical axis C, as e.g. may be seen in FIG. 2. The extension along the central geometrical axis C is preferably uniform as seen along the circular shape around the central geometrical axis C, as e.g. may be seen in FIG. 2.

[0075] As e.g. shown in FIG. 5, the bearing surface 6 may have a convex cross-sectional shape, as seen in a radial plane extending radially from the central geometrical axis C of the support ring 5. The shape is convex in the sense that a central portion of the bearing surface 6, as seen along the central geometrical axis C, of the bearing surface 6 bulges inwardly towards the central geometrical axis C. The convex shape is preferably uniform as seen along the bearing surface 6 extending around the central geometrical axis C. In the disclosed embodiment, the support ring 5 is shaped from a rod having a circular cross-section being bent into a circle. Thereby a convex bearing surface 6 is achieved in a robust and straight-forward manner. It may be noted that the bearing surface 6 may be machined to the convex cross-sectional shape. The bearing surface 6 may e.g. be based on a circular rod and be machined to provide a smoother surface than the surface formed by the circular rod as such. Such machined bearing surface 6 may e.g. have a radius of curvature being greater than the radius of the circular cross-section of the rod. The support ring may also be machined from a solid block such as a circular disk.

[0076] The support ring 5 may be made of a hard material which has durable properties. This material may for instance be a metal, as well as another material with similar durable properties. It may be noted that the support ring 5 may be manufactured from one material and the bearing surface 6 may be manufactured from another material. In such a case, the bearing surface 6 may e.g. be formed of an inlay, such as an internal bushing. In such a case, the material of the bearing surface 6 is typically harder and more wear-resistant than the material from which the body of the support ring 5 is formed.

[0077] The bearing surface 6 may be configured to allow the lower portion of the rotatable shaft 2 to slidable move up and down relatively to the bearing surface 6. The rotatable shaft 2 is slidable movable up and down in a longitudinal direction of the shaft axis L relative the bearing surface 6. It may in this context be noted that during normal operation, the agitator shaft 2 as such does typically not move up and down. However, the fact that the lower portion of the rotatable shaft 2 is slidable movable relative to the bearing surface 6 facilitates installation. Moreover, it makes it easy to provide the non-circularity by tilting the support ring 5 with its bearing surface 6. This is so since a tilted support ring 5 results in that the point of contact moves up and down on the lower portion of the support shaft 2, and by allowing the lower portion of the rotatable shaft 2 to be slidable movable relative to the bearing surface 6, the movement of the contact point is easily accommodated.

[0078] The bearing surface 6 may have a continuous cross-sectional shape, as seen in a radial plane extending radially from the central geometrical axis C of the support ring 5. This achieves the slidable movability of the lower portion of the rotatable shaft 2 relative to the bearing surface 6. The continuous cross-sectional shape of the bearing surface 6 provides a smooth surface in a vertical direction. The bearing surface 6 is thus free from irregularities such as steps and projections in a vertical direction,

[0079] The convex cross-sectional shape of the bearing surface 6 may also achieve and facilitate the slidable movability of the lower portion of the rotatable shaft 2 relative to the bearing surface 6.

[0080] The lower portion of the agitator shaft 2 may be provided with a bushing 10. The bushing 10 is configured to interact with the bearing surface 6 of the shaft support 1. The bushing 10 may be composed of a food grade material, since the applications of an agitator 3 often is used in food industry as well as industries where there is a high demand on good hygiene. A food grade material must be able to be easily and efficiently cleaned. The material is typically not allowed to emit toxins or small pieces of material. It is also an advantage if the material is able to slide with a low friction. Materials which fulfill these requirements are for examples a polymer-based or a ceramic-based materials.

[0081] The bushing 10 may be made of a material being softer than the material forming the bearing surface 6. When the bushing 10 is acting on the curvature of the bearing surface 6 friction will be accomplished. Thereby there is provided a greater tendency towards that the bushing 10 is to be replaced more often than the support ring 5. Since the bushing 10 at the lower portion of the agitator shaft 2 is comparably easy to replace, it is beneficial for the maintenance of the agitator 3 to have a bushing 10 being formed of a material being softer than the material chosen for the bearing surface 6.

[0082] The agitator 3 may be designed such that there is a a radial play between the bearing surface 6 and the lower portion of the agitator shaft 2 as may be seen e.g. in FIGS. 3a and 3b. If a bushing 10 is present, the agitator 3 may be designed such that there is a radial play between the bearing surface 6 and the bushing 10 at the lower portion of the agitator shaft 2. It may be noted that when the agitator shaft 2 rotates, it will typically abut somewhere on the bearing surface 6 inside the support ring 5, such that there is not a radial play around the complete circumference. However, the radial play will typically move around the inside of the support ring 5. Moreover, if the tank is emptied and cleaned, any cleaning fluid will act on the agitator shaft 2 and will typically move the agitator shaft 2 such that the cleaning fluid during the cleaning cycle will get access to all points of the bearing surface 6.

[0083] The bearing surface 6 may define a smallest geometrical cylinder of free space along the shaft axis L. The smallest geometrical cylinder of free space may have a diameter being larger than the diameter of the lower portion of the agitator shaft 2. If a bushing 10 is present, the smallest geometrical cylinder of free space may have a diameter being larger than the diameter of the bushing of the lower portion of the agitator shaft 2. Preferably, the smallest geometrical cylinder of free space has a diameter being at least 1% larger, more preferably 5% larger, than the diameter of the lower portion of the agitator shaft 2 or the bushing 10.

[0084] It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.

[0085] The shaft support 1 may for instance have a differently designed support structure. It may e.g. have a different number of rods. It may e.g. have a ring structure interconnecting the lower ends of the rods. It may e.g. be designed as a box-structure, e.g. partly open or completely closed.

[0086] The number of agitator blades 7 may also differ due to the application and typically dependent on the solution that should be agitating. For example, the number of agitator blades may be 2, 3, 4, 5, 6 or more. The agitator blades 7 may further be of various shapes, sizes and material. The ring 17 which the agitator blades 7 are connected to could either be fixed or movable. The agitator blades 7 may be connected directly to the agitator shaft 2.

[0087] The diameter of the agitator shaft 2 and/or the distribution of the agitator blades 7 may vary along the agitator shaft 2.

[0088] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.