Rotary Bearing with a Damper and a Motor and a Rotary Atomizer with Such Bearing, and Use Thereof

Abstract

A rotary bearing with a damper having an inner bearing element configured for rotation around an axis of rotation, an outer bearing element coaxial with the inner bearing element, an inner damper element with an outer surface surrounding the outer bearing element, an outer damper element with an inner surface surrounding the inner damper element, at least one sealing element provided between the outer surface and the inner surface, the sealing element confining a damper space having a circumferential film space defined by a clearance between the outer surface and the inner surface. The damper space contains fluid and is a closed, isolated damper space.

Claims

1-21. (canceled)

22. A rotary bearing with a damper and with an axis of rotation, comprising: an inner bearing element; an outer bearing element coaxial with the inner bearing element, the inner bearing element configured for rotation around the axis of rotation relative to the outer bearing element; an inner damper element with an outer surface surrounding the outer bearing element; an outer damper element with an inner surface surrounding the inner damper element; at least one sealing element provided between the outer surface of the inner damper element and the inner surface of the outer damper element, said sealing element confining a damper space comprising at least a film space provided by a clearance between said outer surface and said inner surface, the damper space being at least partially filled with fluid, wherein in an operating condition said damper space is a closed, isolated damper space, wherein the damper space is provided with a closable filling port.

23. A rotary bearing with a damper, according to claim 22, wherein the closable filling port is closed by a plug.

24. A rotary bearing with a damper, according to claim 22, wherein two sealing elements confining between them said damper space.

25. A rotary bearing with a damper according to claim 22, wherein said film space is a circumferential film space encircling the inner damper element.

26. A rotary bearing with a damper according to claim 22, wherein said damper space comprises at least two sections comprising said film space and a reservoir space adjacent the film space.

27. A rotary bearing with a damper according to claim 26, wherein said film space is a circumferential film space encircling the inner damper element, and the reservoir space comprises a circumferential part adjacent the circumferential film space.

28. A rotary bearing with a damper, according to claim 22, wherein the damper space is partially filled with liquid and partially filled with gas.

29. A rotary bearing with a damper, according to claim 22, wherein the inner damper element is configured to slide in a direction parallel to the axis of rotation relative to the outer damper element.

30. A rotary bearing with a damper, according to claim 29, wherein the inner damper element is configured to slide in said direction against a bias.

31. A rotary bearing with a damper, according to claim 30, wherein said bias is provided by at least one spring member.

32. A rotary bearing with a damper, according to claim 22, wherein the damper space is provided with a closable vent.

33. A rotary bearing with a damper, according to claim 22, wherein the sealing elements are compressed by one of 5 to 40%; and 10 to 30%.

34. A rotary bearing with a damper, according to claim 22, wherein at least one of the sealing elements is of an elastic material.

35. A rotary bearing with a damper, according to claim 22, wherein a stand-still pressure inside the damper space is atmospheric.

36. A rotary bearing with a damper, according to claim 22, wherein said clearance providing the circumferential film space is in the range of 10 to 2000 μm.

37. A rotary bearing with a damper, according to claim 22, wherein the bearing with the damper is configured for the inner bearing element to rotate at one of 6,000 to 80,000 rpm; and 12,000 to 80,000 rpm.

38. A rotary bearing with a damper, according to claim 22, wherein the axis of rotation in an operating position is vertical.

39. A motor comprising a rotary bearing with a damper and with an axis of rotation, said rotary bearing comprising: an inner bearing element; an outer bearing element coaxial with the inner bearing element, the inner bearing element configured for rotation around the axis of rotation relative to the outer bearing element; an inner damper element with an outer surface surrounding the outer bearing element; an outer damper element with an inner surface surrounding the inner damper element; at least one sealing element provided between the outer surface of the inner damper element and the inner surface of the outer damper element, said sealing element confining a damper space comprising at least a film space provided by a clearance between said outer surface and said inner surface, the damper space being at least partially filled with fluid, wherein in an operating condition said damper space is a closed, isolated damper space, wherein the damper space is provided with a closable filling port.

40. A rotary atomizer comprising a rotary bearing with a damper and with an axis of rotation, said rotary bearing comprising: an inner bearing element; an outer bearing element coaxial with the inner bearing element, the inner bearing element configured for rotation around the axis of rotation relative to the outer bearing element; an inner damper element with an outer surface surrounding the outer bearing element; an outer damper element with an inner surface surrounding the inner damper element; at least one sealing element provided between the outer surface of the inner damper element and the inner surface of the outer damper element, said sealing element confining a damper space comprising at least a film space provided by a clearance between said outer surface and said inner surface, the damper space being at least partially filled with fluid, wherein in an operating condition said damper space is a closed, isolated damper space, wherein the damper space is provided with a closable filling port.

41. A rotary atomizer according to claim 40, comprising a vertical spindle, an atomizer wheel at a lower end of the spindle, a motor at an upper end of the spindle, said motor comprising a rotor, rotary bearings supporting the spindle and the rotor of the motor, wherein at least one of said bearings is a rotary bearing with a damper and with an axis of rotation, said rotary bearing comprising: an inner bearing element; an outer bearing element coaxial with the inner bearing element, the inner bearing element configured for rotation around the axis of rotation relative to the outer bearing element; an inner damper element with an outer surface surrounding the outer bearing element; an outer damper element with an inner surface surrounding the inner damper element; at least one sealing element provided between the outer surface of the inner damper element and the inner surface of the outer damper element, said sealing element confining a damper space comprising at least a film space provided by a clearance between said outer surface and said inner surface, the damper space being at least partially filled with fluid, wherein in an operating condition said damper space is a closed, isolated damper space, wherein the damper space is provided with a closable filling port.

42. A rotary bearing with a damper according to claim 22, wherein the rotary bearing is supporting an element rotating at one of 1,000 to 80,000 rpm; and 12,000 to 80,000 rpm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In the following the invention will be explained in further detail by way of non-limiting examples of embodiments having reference to the accompanying drawings, in which

[0039] FIG. 1 shows a vertical section of a rotary atomizer;

[0040] FIG. 2 shows a vertical section of an embodiment of a motor according to the invention for the rotary atomizer of FIG. 1;

[0041] FIG. 3 shows an enlarged detail indicated by III of the motor shown in FIG. 2; and

[0042] FIG. 4 shows an enlarged view of an embodiment of a bearing shown in FIG. 3.

DETAILED DESCRIPTION

[0043] FIG. 1 shows a rotary atomizer generally of prior art that may be provided with one or more rotary bearings according to the present invention. The rotary atomizer is designed for installation in the upper part of a spray drying chamber and comprises a support bracket 1 for connection with a ceiling wall of the spray drying chamber. The support bracket 1 supports a casing bottom 2′ of a drive motor 2 e.g. in the form of a high frequency asynchronous electric motor. A feed pipe 4 for the supply of the product to be atomized extends downwards through a lower atomizer casing 5 to terminate at an atomizer wheel 6. The atomizer wheel 6 is secured at the lower end of a drive shaft 7 designed as a relatively slender solid spindle which is radially supported by bearings 9 and 10. The lower bearing 10 also serves as an axial support of the drive shaft or spindle 7. The motor 2 comprises a motor shaft 11′, which at a lower shaft end 12′ is connected to the drive shaft 7 through a coupling 13 comprising in a manner known per se an upper coupling part connected to the motor shaft 11′ and a lower coupling part connected to the drive shaft 7.

[0044] FIG. 2 shows a drive motor 20 according to the present invention that may substitute the drive motor 2 shown in FIG. 1. Thus, the drive motor 20 comprises a motor shaft 11 with a lower shaft end 12 for connection to the coupling 13 shown in FIG. 1.

[0045] Further the drive motor 20 comprises a casing bottom 21 for connection to the support bracket 1, a generally cylindrical casing side part 22 and a casing top part 23. The casing bottom 21 and the casing top part 23 may e.g. be connected to the casing side part 22 by means of screws 24 (omitted in FIG. 3).

[0046] The motor shaft 11 has a vertical axis of rotation A and carries a rotor winding 25 that is surrounded by a stator winding 26 (se FIG. 3, omitted in FIG. 1). The motor shaft 11 is supported relative to the casing bottom 21 and the casing top part 23, respectively, through rolling element bearings, which in the embodiment shown are ball bearings 27, 28, but alternatively roller bearings might be used for one or both of these two bearings. Thus, lower ball bearing 27 is supports the lower shaft end 12 radially and axially relative to the casing bottom 21 and upper ball bearing 28 supports an upper shaft end 29 of the motor shaft 11 relative to the casing top part 23.

[0047] In the embodiment shown the upper ball bearing 28 is incorporated in a rotary bearing with a damper 19 according to the present invention as will be explained in the following having reference to FIGS. 3 and 4.

[0048] FIGS. 3 and 4 show the upper shaft end 29 and a portion of the casing to part 23. The ball bearing 28 comprises an inner bearing element 30 seated on the upper shaft end 29, and configured for rotation around the axis of rotation A together with the motor shaft 11. An outer bearing element 31 is coaxial with the inner bearing element 30 and between these two bearing elements balls 32 are positioned as it is known in the art. The bearing 28 is sealed and greased as it is per se known in the art and thus the bearing is of the kind which is delivered in so-called life-time greased condition.

[0049] In the present embodiment the outer bearing element 31 is seated in an inner damper element 33 with an outer surface 34. Alternatively, the outer bearing element 31 might be an integral part of the inner damper element 33. An outer damper element 35 with an inner surface 36 is surrounding the inner damper element 33. In the present embodiment the outer damper element 35 is an integral part of the casing top part 23. Two sealing elements 37, which in the present embodiment are seals of elastic material, e.g. O-rings, are provided between the outer surface 34 of the inner damper element 33 and the inner surface 36 of the outer damper element 35. The sealing elements 37 are in the present embodiment mounted or seated in recesses in the inner surface 36 of the outer damper element 35 and abut against the outer surface 34 of the inner damper element, which in the present embodiment is cylindrical.

[0050] The sealing elements 37 are confining between them a damper space 38 with at least two sections comprising a, generally cylindrical, circumferential film space 38a defined by a clearance between the outer surface 34 of the inner damper element 33 and the inner surface 36 of the outer damper element 35, and a reservoir space 38b comprising at least a circumferential part 38c adjacent the circumferential film space 38a. The clearance providing the circumferential film space, i.e. the distance between the outer surface 34 and the inner surface 36, is e.g. in the range of 10 to 2000 μm.

[0051] The damper space 38 is according to the present invention a closed, isolated damper space.

[0052] The reservoir space 38b is in the shown operating position extending above the circumferential film space 38a. The damper space 38 is provided with a closable filling port 39 constituted by a vertical bore. The filling port 39 is in the operating condition closed by a screw plug 40. Further, the damper space is provided with a closable vent 41 likewise constituted by a vertical bore and closed in the operating condition by a screw plug 42. In the present embodiment, in an operating condition the fluid contained in the damper space 38 is partially liquid such as oil e.g. with a viscosity in the range of 30 to 50,000 cP. To fill the liquid into the damper space the two screw plugs 40 and 42 are removed, the liquid is filled into the filling port 39 while air escapes through the vent 41. In the present embodiment the amount of liquid fills completely the circumferential film space 38a whereas the reservoir space 38b is only partially filled with liquid to contain also an amount of air, or other gas that may be vented in to the damper space 38. The function of this amount of air will be explained below.

[0053] In the embodiment shown, the inner damper element 33 is configured to slide in a direction parallel to the axis of rotation A relative to the outer damper element 35. Thus the outer surface 34 of the inner damper element where the sealing elements 37 abut is smooth, preferably with surface roughness R.sub.a of e.g. 2.5 μm or less to allow the sealing elements to slide along the outer surface 34 parallel to the axis of rotation A.

[0054] The casing top part 23 is provided with a cover 43 and between said cover 43 and the inner damper element 33 a number of springs 44 are provided to bias the inner damper element 33 in a direction towards the casing bottom 21. Preferably the bias should be balanced around the axis of rotation A.

[0055] During operation the temperature of the drive motor 20 including the motor shaft 11 may rise and accordingly the motor shaft may be subject to thermal expansion or extension. Such extension will be absorbed by the inner damper element 33 rising against the force of the springs 44. When operation is stopped and the temperature drops, the thermal extension of the motor shaft 11 reverses. Due to the force or bias of the springs 44, the inner damper element 33 will correspondingly return to its original, lower position.

[0056] In order to close effectively the damper space 38, the sealing elements 37 are, in their mounted or seated condition, compressed by by 5 to 40%, especially by 10 to 30% relative to their relaxed conditions before mounting. Thus the dimension of the cross section of the sealing elements 37 between the outer surface 34 and the inner surface 36, in the mounted or seated condition shown in the figures, is reduced, in a radial direction relative to the axis of rotation A, to 60 to 95%, especially 70 to 90%, of the dimension in an unstressed or relaxed condition. Hereby it is secured that the liquid inside the damper space 38 does not leak during operation. Compressing the sealing elements 37 entails friction between the sealing elements 37 and the outer surface 34. In order to ensure that the inner damper element 33 returns to its original position after operation the spring force or bias of the springs 44 preferably exceed the static friction force between the sealing elements 37 and the outer surface 34.

[0057] Filling liquid into the damper space 38 as explained above entails that the pressure inside the damper space 38 immediately after filling in the liquid, i.e. a stand-still pressure, will be, at least approximately, atmospheric. During operation the rising temperature of the drive motor 20 may spread to the casing top part 23 including the outer damper element 35 and the liquid accommodated in the damper space 38. If the thermal expansion of said liquid is larger than the thermal expansion of the outer damper element 35 an excess expansion of the liquid may be absorbed by the amount gas or air like accommodated in the damper space 38, the pressure inside the damper space 38 rising correspondingly. Thus, this amount of gas or air fulfills the function of an expansion tank or chamber. The person skilled in the art will easily envisage other means of fulfilling the function of an expansion tank or chamber, and accordingly it is envisaged that the damper space 38 may be completely filled with liquid.

[0058] The motor shaft 11 and the drive shaft 7 of the rotary atomizer may be connected through the coupling 13 that provides for slight movement between the motor shaft 11 and the drive shaft 7 while ensuring a uniform speed of rotation of the two shafts. In one alternative the motor shaft and the drive shaft may be integral as disclosed in the above-mentioned EP 2 826 566 A1. In a second alternative the motor shaft and the drive shaft may be connected through a gearing whereby the motor during operation will run with a lower rotational speed than the drive shaft.

[0059] The bearing with the damper 19 may be used in configurations in which the inner bearing element 30 rotates at 1,000 rpm or more, such as 6,000 rpm or more, especially at 12,000 rpm or more e.g. at 40,000 to 60,000 rpm, and even up to 80,000 rpm.

[0060] During rotation of an element seated by means of a bearing with a damper according to the present invention vibrations will occur, especial at specific speeds of rotation, known in the art as critical speeds of rotation. Using a damper, it is possible to accelerate a rotating element to pass at least some critical speeds to run the element at a higher rotational speed than said critical speeds, the vibrations that would normally occur at said critical speed being damped to an acceptable level.

[0061] When damping vibrations, the inner damper element 30 of the present invention will move (slightly) in radial directions perpendicular to the axis of rotation A in relation to the outer damper element 31. During these movements the clearance between the outer surface 34 and the inner surface 36 will increase and decrease in an oscillating manner and the volume between the outer surface 34 and the inner surface 36 within a given angular area around the axis of rotation A will increase and decrease accordingly. In the present embodiment where at least part of the fluid present in the damper space 38 is a liquid, this increasing and decreasing of the clearance at specific angular positions or areas will force the liquid present in the circumferential space 38a to move and some of the liquid will move circumferentially around the axis of rotation A (referred to as “squeeze film effect”), but some of the liquid may at some angular position relative to the axis of rotation A be forced into the adjacent circumferential part 38c of the reservoir space 38b entailing a shortage of liquid at angular positions opposite to the first mentioned angular positions. Such shortage may correspondingly be replenished from the adjacent circumferential part 38c of the reservoir space 38b, at least part of said reservoir space 38b extending above the circumferential film space 38a to provide a (slightly) higher potential energy of the liquid present in the circumferential part of the reservoir space than of the liquid present in the circumferential film space.

[0062] It is noted that while in the embodiment shown in FIGS. 1-3, the inner damper element 33 and the outer damper element 35 are configured to slide relative to each other in a direction of the axis of rotations, and the inner damper element 33 and the outer damper element 35 are capable of minor radial shifts relative to each other as described above, the inner damper element 33 and the outer damper element 35 are substantially prevented from rotating relative to each other by means not shown. Such means will be obvious to the person skilled in the art of so-called squeeze film dampers.