GB2577275A

GB2577275A - Apparatus for supporting a rotor during a balancing process

Info

Publication number: GB2577275A
Application number: GB1815247.0A
Authority: GB
Inventors: Fowler Steve
Original assignee: UNIVERSAL BALANCING Ltd
Current assignee: UNIVERSAL BALANCING Ltd
Priority date: 2018-09-19
Filing date: 2018-09-19
Publication date: 2020-03-25
Anticipated expiration: 2038-09-19
Also published as: GB2577275B; GB201815247D0; WO2020058671A1

Abstract

An apparatus for supporting a rotor 20 during a balance process is described, the apparatus including: a mounting device 12 for connecting to a first end 14 of a rotor to be balanced, the mounting device being rotatably drivable by a driving device 16 for effecting rotation of the rotor about a rotational axis; a support device 18 for supporting a second, opposite, end 22 of the rotor, said support device supporting the second end 22 of the rotor for rotation about the rotational axis, wherein the support device is configured to permit the second end of the rotor to move towards and/or away from the mounting device in the direction of the rotational axis, whilst the rotor is rotating. The support device 18 is provided with pressurized jets of air to allow rotation and movement of the test rotor 20 along the rotational axis note figures 2 and 3.

Description

Title: Apparatus for supporting a rotor during a balancing process

Description of Invention

The present invention relates to an apparatus for supporting a rotor, such as a propshaft, during a balancing process.

The invention has been devised primarily, although not exclusively, in relation to rotors which may include an articulated connection at one or both ends thereof, and in particular to a rotor of the kind which is of a fixed length, i.e. does not include two rotor parts which can slide (known as plunge) relative to each other so as to alter the overall length of the rotor. That said, it should be appreciated that the invention is not exclusive to such rotors and may therefore be utilised for rotors which include plunge and which do not necessarily have articulated connections at their ends.

Propshafts, and more generally rotors, can be formed of a single rotor portion or multiple rotor portions linked together in end-to-end alignment. Rotors formed of multiple rotor portions may comprise two or three such portions, and less commonly may comprise four portions.

Balancing is typically carried out on rotors to overcome or lessen the problem of unbalance the uneven distribution of mass around the axis of rotation of the rotor. Unbalance is when the inertia axis of the rotor is offset from its central axis of rotation, which results from the mass of the rotor not being distributed uniformly about its central axis. Rotors suffering unbalance may generate a moment when rotating which leads to vibration.

It is known to balance a single piece rotor using two balance planes. Each balance plane is a plane disposed substantially perpendicular to the axis of the rotor. When balancing a multiple piece rotor, balancing is carried out in additional balance planes: a two piece rotor may be balanced in three planes, a three piece rotor may be balanced in four planes, and a four piece rotor may be balanced in five planes.

Correction for unbalance is typically carried out by welding or attaching balance weights to the rotor. Rotors are designed with zones where balance weights can be added corresponding to the number of balancing planes, which are usually near the end of each rotor portion.

The mechanism for correcting unbalance is typically automated, by which balance weights are attached (e.g. welded) to the rotor at a set position along the axis of the rotor for each plane, within specified balance zones. Once weights for all planes (where required) are applied to the rotor, the rotor unbalance is measured again using the same method. If the unbalance measured in any plane remains outside of a predefined tolerance threshold, a second step of correction is carried out within the corresponding balance zone.

To perform the balancing process a rotor is loaded into a balancing machine that includes an apparatus for driving and supporting the rotor. In prior art balancing machines, each end of the rotor is located in a respective mounting apparatus that includes a chuck or the like to secure that end of the rotor. The mounting apparatuses are driven by a drive mechanism so as to transfer torque to the rotor.

Problems can arise when the rotor is made of certain materials, especially if it includes articulated connections at its ends. In such a rotor, fixing each articulated end, e.g. part of a universal joint, in a chuck or the like can result in the frequency of the rotor changing during the balancing process, i.e. when the rotor is rotated at the desired balancing speed. If as a result of the resilient clamping of the rotor in the machine, the frequency of the rotor changes during balancing to a frequency which corresponds to the balancing speed/frequency, then the rotor is excited and the resulting vibrations renders the measuring of unbalance difficult or impossible. Unbalance and rotor defection (due to it being in or near resonance) also adds to the problem (of not being able to measure unbalance) if the shaft has no axial movement (e.g. no plunge).

The present invention has been devised to address this problem.

According to a first aspect of the invention we provide an apparatus for supporting a rotor during a balance process, the apparatus including: a mounting device for connecting to a first end of a rotor to be balanced, the mounting device being rotatably drivable by a driving device for effecting rotation of the rotor about a rotational axis; a support device for supporting a second, opposite, end of the rotor, said support device supporting the second end of the rotor for rotation about the rotational axis, wherein the support device is configured to permit the second end of the rotor to move towards and/or away from the mounting device in the direction of the rotational axis, whilst the rotor is rotating.

According to a second aspect of the invention we provide a system for balancing a rotor, the system including an apparatus according to the first aspect of the invention and a rotor to be balanced, the rotor including a first end and a second opposite end.

Further features of the first and second aspects of the invention are set out in the claims appended hereto.

Embodiments of the invention will now be described, by way of example only, with reference to the following figures, of which: Figure 1 is a side view of a system for balancing a rotor including an apparatus according to the present invention; Figure 2 is an end view of a support device for supporting a second end of the rotor; Figure 3 is a close up side view of the support device of figure 2 supporting the second end of the rotor; Figure 4 is a side view of a second embodiment of a system including an apparatus for supporting a rotor in accordance with the present invention; Figure 5 is an end view of a support device for supporting a second end of the rotor; Figure 6 is a close up side view of the support device of figure 5; Figure 7 is side view of a support device of a third embodiment of the invention.

Referring firstly to figures 1 to 3, these show a first embodiment of a system and apparatus in accordance with the present invention. The system shown is for balancing a rotor 20 so as to measure any unbalance therein and then, as a subsequent step, to correct for that unbalance. In this particular example the rotor 20 to be balanced has first 14 and second 22 ends in the form of first and second articulated joints or universal joints, which are connected to each other by elongate rotor portion 20a. It should be appreciated that the system and apparatus in accordance with the invention may be utilised in relation to rotors of different configurations than that shown. For example, it may be utilised in relation to rotors with only one articulated joint at one end thereof or with no articulated joints. In addition, whilst the invention has been devised primarily in relation to a rotor which is of a fixed length, i.e. does not include two rotor parts which can slide or plunge relative to one another, the invention may be utilised in balancing a rotor that does include such a plunge connection. In the present example the rotor is made from Aluminium, but it could be made from another material.

In more detail, the system includes an apparatus 10, the purpose of which is to support the rotor 20 during the balancing process. In order to achieve this the rotor 20 is supported at its ends so that it can rotate about a generally horizontal rotor axis A, although it should be appreciated that the axis of rotation need not be horizontal it would be vertical. In order to provide for such rotational support, the apparatus 10 includes a mounting device, indicated generally at 12, which supports the first end 14 of the rotor 20, and a support device 18 which supports the second, opposite, end 22 of the rotor 20.

The mounting device 20 is of the kind well known in the art and includes a driving device 16, e.g. a motor or the like, for effecting rotation of the rotor 20 about the rotational axis A. The motor 16 is drivingly connected to a chuck or the like 13 which can be tightened so as to grasp an end portion of the first end 14 of the rotor. The mounting device 14 is spaced above and connected to a main body 11 of the apparatus 10 by way of a support 17, which, preferably, can translate along the main body 11 by way of a rail connection 11 a.

At an opposite end of the main body there is provided a further support 19 which supports a support device 18. Figures 2 and 3 show this support device 18 in more detail, from which it can be seen that an end portion 23 of the articulated joint provided at the second end 22 of the rotor 20 is supported for rotation within a generally cylindrical passage 31. The generally cylindrical passage 31 includes an interior surface 32 which in use faces an exterior surface of the rotor portion 23. An internal diameter of the generally cylindrical passage 31 is greater than the external diameter of the portion 23. The support device 18 is advantageously provided with a plurality of air jet devices 33 which are configured to direct a pressurised source of air (not shown) into a gap between the interior surface of the generally cylindrical passage 31 and the exterior surface of the portion 23. These pressurised jets of air are sufficient so as to maintain a gap between the interior surface 32 of the cylindrical passage 31 and the exterior surface of portion 23, whilst the rotor is rotating. Thus, a relatively frictionless interface is provided between the support device 18 and the end portion 23, meaning that the rotor 20 is free to rotate about the rotational axis A when driven by the motor 16.

Advantageously, the configuration of the support 18 is such that is permits the second end 22 of the rotor 20 to move relative thereto towards and/or away from the mounting device 12 in the direction of the rotational axis A, whilst the rotor is rotating. That direction is shown on figure 3 with the double-ended arrow B. In this particular embodiment the movement between the rotor end portion 23 and the support device 18 is a sliding connection, with the end portion 23 sliding into and out from the generally cylindrical passage 31. Of course it should be appreciated that during balancing the movement of the second end 22 of the rotor 20 in the direction of the double-ended arrow B is not considerable, but in providing for such axial movement improved measuring of imbalance in the rotor 20 can be achieved. It should be appreciated that providing and maintaining of the air gap between the interior surface 32 of the passage 31 and the exterior surface of the rotor portion 23 provides for this sliding movement whilst at the same time preventing or at least inhibiting the second end 22 of the rotor 20 from moving substantially radially away from the rotational axis A. Minimising any movement in the radial direction, that is in the direction which is perpendicular to the rotational axis A, is important as it is in this direction that the amount of unbalance is measured.

It should be noted that in the present embodiment both the support device 18 and the mounting device 12 include or are connected to separate means for sensing or determining an amount of unbalance in a balancing plane positioned at or near respective ends of the rotor 20. Such sensing may be achieved by way of or within the supports 17, 19 or in some other components connected to the support device 18 and/or the mounting device 12.

Referring to figures 4 to 6, these show a second embodiment of a system and apparatus in accordance with the present invention. Features in common with the first embodiment have been given the same reference numerals as those used in figures 1 to 3, but with the additional of a prime symbol. Those like features will not be described in any further detail herein.

In the embodiment shown in figures 4 to 6, the only difference is the configuration and operation of the support device 18' for supporting the second end 22' of the rotor 20'. Here, instead of providing the air gap around the exterior surface of the end portion 23', the support device 18' includes a projection 41, which in this example is an adjustable collet or the like which is received in a generally centrally extending recess in an end of the rotor portion 23'. It should be appreciated that whilst the collet 41 in this particular embodiment is a male which is received in a female formation on the rotor 20', it could be provided as a female formation which receives the end of the rotor portion 23'.

In more detail, the support device 18' includes a pair of bearing devices 42 which support and permit the collet 41 to rotate about the rotational axis A. Thus, when the collet is positioned within the end of the rotor portion 23' the rotor is free to rotate by way of the motor 16' about the rotational axis A. In order to provide for the second end 22' of the rotor 20' to move towards and/or away from the mounting device 12' in the direction of the rotational axis A, whilst the rotor 20 is rotating, the support device 18' is provided with a pair of flexible support members 43 which are positioned adjacent and spaced from each other along the rotational axis A and are both supported on the support 19'.

In end view each flexible member 43 includes a base portion 46 which extends generally horizontally and a pair of generally upright extending portions 45 which are spaced underneath but to either side of the rotational axis A. Each upright portion 45 terminates an upper end 42. The flexible members 43 in this embodiment are made from a metallic material, for example steel, and are configured so as to permit the collet 41 to resiliently move towards and away from the mounting device 12 whilst the collet 41 and the rotor 20 are rotating. This resilient movement is effectively provided by way of the members 43 flexing about their connection to the support 19' in the direction shown by the double-sided arrow C. In a similar fashion to the first embodiment, both the mounting device 12' and the support device 18' include or are connected to means for sensing or determining an amount of unbalance in a balancing plane positioned at or near each end of the rotor 20. Also, it should be noted that advantageously the configuration of the flexible members 43 ensure that the second end 22' of the rotor 20' is able to move towards and/or away from the mounting device 12' in the direction of the rotational axis A, whilst the rotor 20' is rotating, but whilst also preventing or at least inhibiting the second end 22' of the rotor 20' from moving substantially radially away from the rotational axis A. This ensures that accurate unbalance can be sensed or determined when the balancing process is taking place.

Referring to figure 7, this shows a third embodiment of the invention, which engages with the end of the rotor in a similar fashion to the second 30 embodiment. Features in common with the first and second embodiments have been given the same reference numerals but with the additional of two prime symbols ( ). Those like features will not be described in any further detail herein.

The support device 18 permits the second end 22 of the rotor 20 to rotate about the axis A in a similar fashion to the second embodiment, but the means for allowing for some axial movement thereof, but whilst also inhibiting or at least preventing radial movement of the second end 22 of the rotor relative to the axis A, is achieved in a different way. In the third embodiment, there is provided a linear bearing device 60, which is positioned under and supports the pair of bearing devices 42. The linear bearing 60 is configured so as to permit bearing devices 42 and the collet 41 to move towards and away from the mounting device (not shown whilst the collet 41 and the rotor 20 are rotating. This movement is in the direction shown by the double-sided arrow B. In a yet further embodiment, the linear bearing functionality and the rotational bearing functionality may be combined into a single device or pair of devices.

In a yet further embodiment, a magnetic bearing or the like could be provided at the support device end of the apparatus/system, in the case where the rotor (or at least the end of the rotor) was a magnetically susceptible material, e.g. steel. Such a magnetic bearing would provide a similar functionality to the first embodiment, where an air gap is provided between the magnetic bearing and the exterior surface of the end portion of the rotor, whilst permitting the second end of the rotor to move towards and away from the mounting device.

Whilst in the first, second and third embodiments discussed above there are shown specific configurations to support the second end of the rotor whilst allowing that end towards and away from the mounting device, it should be appreciated that other configurations of the supporting device may be utilised without departing from the scope of the invention. All that is required is for the support device to permit the second end of the rotor to rotate about the axis A and allow for some axial movement thereof, but whilst also inhibiting or at least preventing radial movement of the second end of the rotor relative to the axis A. Whilst not shown, the systems and apparatus discussed above may include devices for attaching balancing weights to the rotor as part of the balancing process.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS1. An apparatus for supporting a rotor during a balance process, the apparatus including: a mounting device for connecting to a first end of a rotor to be balanced, the mounting device being rotatably drivable by a driving device for effecting rotation of the rotor about a rotational axis; a support device for supporting a second, opposite, end of the rotor, said support device supporting the second end of the rotor for rotation about the rotational axis, wherein the support device is configured to permit the second end of the rotor to move towards and/or away from the mounting device in the direction of the rotational axis, whilst the rotor is rotating.
2. An apparatus according to claim 1 wherein the support device prevents or at least inhibits the second end of the rotor from moving substantially radially away from the rotational axis, whilst the rotor is rotating.
3. An apparatus according to claim 1 or 2 wherein the support device includes or is connected to means for sensing or determining an amount of unbalance in a balancing plane positioned at or near the second end of the rotor.
4. An apparatus according to claim 1, 2 or 3 wherein the mounting device includes or is connected to means for sensing or determining an amount of unbalance in a balancing plane positioned at or near the first end of the rotor.
5. An apparatus according to any preceding claim wherein the support device is configured to permit the second end of the rotor to move relative 30 thereto towards and/or away from the mounting device in the direction of the rotational axis, whilst the rotor is rotating.
6. An apparatus according to claim 5 wherein the support device is configured to permit the second end of the rotor to slide relative thereto towards and/or away from the mounting device in the direction of the rotational axis, whilst the rotor is rotating.
7. An apparatus according to claim 5 or 6 wherein the support device includes a generally cylindrical passage which receives the second end of the rotor and wherein the generally cylindrical passage includes an interior surface which faces an exterior surface of the second end of the rotor.
8. An apparatus according to claim 7 wherein the generally cylindrical passage has an internal diameter which is greater than an external diameter of the rotor to be balanced.
9. An apparatus according to claim 7 or 8 wherein the support device is configured, in use, to maintain a gap between the interior surface of the generally cylindrical passage and the exterior surface of the second end of the rotor.
10. An apparatus according to claim 9 wherein the support device utilises air under pressure to maintain said gap.
11. An apparatus according to any one of claims 1 to 4 wherein the support device includes a connection device for connecting the support device to the second end of the rotor.
12. An apparatus according to claim 11 wherein the connection device provides a rotationally fast connection with the second end of the rotor and 30 preferably includes one or more bearing members for permitting the connection device to rotate with the rotor about the rotational axis.
13. An apparatus according to claim 11 or 12 wherein the connection device is permitted to move towards and/or away from the mounting device, whilst the connection device and the rotor are rotating.
14. An apparatus according to claim 13 wherein the connection device is resiliently movable towards and/or away from the mounting device, whilst the connection device and the rotor are rotating.
15. An apparatus according to claim 13 or 14 wherein the connection device is supported for such movement by one or more flexible members.
16. An apparatus according to claim 15 wherein the flexible member(s) is connected at one end to the connection device and is connected or connectable at another end to a fixed body.
17. An apparatus according to any one of claims 11 to 16 wherein the connection device is configured to engage with a male or female end portion of the second end of the rotor, e.g. by way of a chuck or the like.
18. An apparatus according to any preceding claims wherein the system includes a main body which at one end supports the mounting device and at another end supports the support device.
19. A system for balancing a rotor, the system including an apparatus according to any preceding claim and a rotor to be balanced, the rotor including a first end and a second opposite end.
20. A system according to claim 19 wherein the first end includes a first portion which is connected to the remainder of the rotor by a first articulated joint
21. A system according to claim 20 wherein the second end includes a second portion which is connected to the remainder of the rotor by a second articulated joint
22. A system according to claim 21 wherein the first and second articulated joints are connected by an elongate rotor portion.
23. A system according to claim 22 wherein the elongate rotor portion is a single, e.g. non-plunged, rotor portion.