GB1595510A

GB1595510A - Dynamic balancing machine

Info

Publication number: GB1595510A
Application number: GB20604/78A
Authority: GB
Original assignee: Avery Denison Ltd
Current assignee: Avery Denison Ltd
Priority date: 1978-01-20
Filing date: 1978-05-19
Publication date: 1981-08-12
Also published as: JPS6217687B2; DE2802367A1; JPS5536786A; DE2802367B2; DE7801587U1; IT7919318A0; FR2415295A1; FR2415295B1; IT1110934B

Description

(54) AN IMPROVED DYNAMIC BALANCING MACHINE (71) We, AVERY-DENISON LIMITED, of Smethwick, Warley, West Midlands B66 2LP, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a dynamic balancing machine with bearing pedestals disposed on a machine bed to support rotors which are to be balanced, each comprising a vibrating bridge carrying a bearing for the rotor and a base body, together with a processing unit carrier running parallel to the longitudinal axis of a rotor supported by the bearing pedestals.

Previous machines for the dynamic balancing of rotors utilised bearing pedestals wherein the bearing for the rotor is disposed on a vibrating bridge mounted by springs on a base body. Such bearing pedestals can only be utilised with considerable difficulty especially when heavy rotors such as the rotors in electrical generators, or drive shafts or crankshafts require to be balanced, since the bearing is disposed above the centre of the base body. Because of this fact, additional free space must be provided above the bearing so that the body to be balanced can be inserted into the bearing from above, using a crane or like loading device.

There are also considerable difficulties in correcting the unbalance, since processing units such as welders or grinders cannot be disposed within the reach of the operative engaged in correcting the unbalance. Nor are the processing units movable perpendicular to the longitudinal axis of the rotors, hence their position can only be altered between the bearing pedestals.

Apart from the difficulties in loading and unloading heavy rotors in a bearing pedestal, there is also a risk-especially with elongated rotors-of permanent deformation through the critical rotary speed being reached.

The value of the critical rotary speed is independent of the bearing pedestal design; however only one critical rotary speed can be picked up by the transducer used for measurement, while the other critical rotary speed acting perpendicularly thereto can cause damage, firstly because it appears at a lower rotary speed and secondly because it is not recognised by the transducer.

Based on this prior art, the invention is based on the aim of making operation of a dynamic balancing machine simple and reliable.

According to the present invention we provide a dynamic balancing machine with bearing pedestals disoosed on a machine bed to support rotors which are to be balanced, each pedestal comprising a base body and a vibrating bridge which carries a bearing for the rotor and is mounted on the base body by a pair of vertical leaf springs, said bearings being arranged so as to locate, in use, the rotor with its longitudinal aixs offset from and parallel to a plane extending medially with respect to each pair of leaf springs, said machine further including a processing-unit carrier running parallel to said longitudinal axis.

This offsetting of the longitudinal axis of the rotor enables loading of the dynamic balancing machine with rotors requiring balancing to be effected directly by the operative, and also the operative himself can perform his functions with the workpiece immediately adjacent his body, especially with light drive shafts, without having to make additional movements away from the body.

In one particular embodiment of the invention, the longitudinal axis of the rotor is disposed above the base bodies of the pedestals. With this disposition of the longitudinal axis of the rotor, positioning of the individual rotors requiring balancing is greatly facilitated, especially when the bearing pedestal is being supplied with workpieces from lifting equipment.

In a further embodiment of the invention, it is proposed that the longitudinal axis of the rotor be disposed above a vertical end face of the base body. The particular advantage of this embodiment is that this type of bearing can also be used at very high rotor speeds, as used for instance in balancing drive shafts.

Yet a further embodiment of the invention proposes that the longitudinal axis of the rotor be disposed horizontally offset from the vertical end face of each base body. This embodiment is particularly suitable for use in low-speed dynamic balancing, while maintaining all the benefits of easy operation mentioned above. In an embodiment of the invention especially for the balancing of drive shafts it is proposed that the mass of each vibrating bridge is appreciably greater than the proportion of the rotor mass supported by the bearing of the bridge.

Because of the large mass of the vibrating bridge, the differences in the critical bend of the test rotor in various directions, due to the differing stiffness of the leaf springs in different directions, are so much reduced that even the critical bend resonance occurring at a higher rotary speed can already be recognised when the critical bend resonance at a lower rotary speed has not yet reached its maximum.

In another embodiment of the invention especially for the dynamic balancing of rotors which may vary greatly among themselves in axial length, it is proposed that the carrier be movable perpendicularly to said longitudinal axis. The advantage of such an arrangement is that the processing units can be brought without difficulty into the working area between the bearing pedestals, and if necessary can also be located outside these pedestals. This makes it also possible to provide free space for the loading of the balancing machine by lifting equipment.

The invention will be explained in more detail with reference to the attached drawings.

In these:- Figure 1 shows an elevational view of a bearing pedestal for a dynamic balancing machine in accordance with the invention, Figure 2 is an elevational view of a further bearing pedestal for a dynamic balancing machine in accordance with the invention, Figure 3 is a dynamic balancing machine having two bearing pedestals in accordance with the invention for the balancing of crankshafts, and a carrier for supporting machining units, Figures 4 and 5 show alternative forms of two different machining units.

According to Figure 1 a base body 1 disposed on a machine bed 2 supports, via leaf springs 3 and 4 disposed in parallel, a vibrating bridge 7, the leaf springs 3 and 4 being fixedly connected to the base body 1 and the vibrating bridge 7. On the vibrating bridge 7 is disposed a bearing 8 for the rotor being examined, with the longitudinal axis 9 of the bearing 8 being offset from and parallel to a plane 10 extending medially of the leaf springs 3 and 4 and passing through the centres of the bridge 7 and the base body. During rotation of a rotor being investigated about the longitudinal axis 9 of bearing 8, the rotor vibrations are converted by a transducer 11 into electrical potentials, and processed in order to determine the unbalance.For this purpose the transducer 11 is only subjected to vibrations in the direction of its longitudinal axis, with all vibrations transverse thereof being suppressed.

The arragement shown in Figure 2 of a bearing pedestal for a dynamic balancing machine is characterised by a displacement of the bearing 8 for the rotor being examined over the vertical end surface 15 of the base body 1. The vibrations transmitted by a rotor 16 to the vibrating bridge 7 are picked up by a transducer 18 which in contrast to the absolute transducer 11 shown in Figure 1, is a relative transducer and are then processed. As seen from the two drawings, any type of transducer can be used to convert the mechanical vibrations into electrical vibrations, so there is no restriction on the nature of the transducer shown.

In Figure 2 a roller bearing 20 is used for carrying the rotor 16, and is particularly suitable for the balancing of rotors with their own bearing journals. Here again the longitudinal axis 9 of the roller bearing 20 is parallel to and displaced from the medial plane 10.

As shown in more detail in Figure 3, the bearing 8 represented in Figure 1 can also be used for the dynamic balancing of rotors which do not themselves possess a support surface.

According to Figure 3 the base bodies 1 of two bearing pedestals are movably mounted on a machine bed 2; the vibrating bridges 7 are oscillatably connected by leaf springs 3, 4 to the base bodies 1. In each of the bearings 8 is disposed a balance spindle 30 whereof one is driven by a motor (not shown) in the dynamic balancing machine. Both bearings 8 carry holders 31 which are connected to the rotor being examined, in the present case a drive shaft 32.

On the machine bed 2 there is also supported a carrier 40 which can move along a guide 41 perpendicular to the longitudinal axis 9 of the drive shaft 32. According to Figure 3 the guides 41 are disposed in holders 42, 43 on the machine bed in such manner that the holder 43 lies outside the right-hand base body 1. With such a device it therefore also becomes possible to balance short drive shafts. If there is a need however to dynamically balance extremely long rotors, the holder 43 can also be disposed to the left or the righthand base body 1, and the carrier 40 can be extended as desired as a free cantilevered carrier.

As shown by Figures 4 and 5, processing units are mounted on the carrier 40. Thus Figure 4 shows a welding apparatus 45 which by means of a support 46 can be moved along the carrier 40, 43, and by movement of the carrier 40 in one of the directions indicated by arrow 47 can be brought into the operating position determined by axis 9.

In Figure 5 the processing unit comprises a driller 48 which by movement in one of the arrow 47 directions can be brought into the vicinity of the machining plane represented by the axis 9.

As already described, for each bearing pedestal a separate transducer 11 or 18 picks up the vibrations of the unbalanced crankshaft 32.

Leaf springs disposed parallel to each other as shown in Figures 1 and 2 are yielding in the direction of the transducers, so that the vibrations of the rotor being examined can be picked up, but are rigid in the direction perpendicular thereto. Due to this arrangement, and especially with an elongated rotation body, shown as a driveshaft 32, there occur two critical bending frequencies-one critical bending frequency in the direction of the transducer and one critical frequency in a direction perpendicular thereto. However the transducer can only pick up bending frequencies acting in its direction and use them for display or further processing. The bending resonance frequency perpendicular hereto occurs at a lower rotary speed, but cannot be brought to display.The resulting danger is that at this critical rotary speed the rotor being examined can already undergo damage, without the operative being able to adjust to this. If each of the two vibrating bridges 7 has an appreciably greater mass than the proportionate share of the rotor weight, the critical resonance frequency in the test direction is reduced to a lower rotary speed, and hence also its difference from the lower critical fequency in a direction perpendicular ito the test direction is reduced. This ensures that before the lower critical frequency arises, the higher critical frequencv operating in the test direction already becomes clearly noted, for example through migration of the unbalance display from a previously adopted position, so that the dynamic balancing rotary speed can be limited in good time and prevent damage occurring.

Particularly with flat based dynamic balance machines, the vibrating bridge 7 may also be integrated in the base body 1 by making this body U-shaped, and displacing the longitudinal axis of the bearing relative to the base body centre 10, within this U-shape.

WHAT WE CLAIM IS: 1. A dynamic balancing machine with bearing pedestals disposed on a machine bed to support rotors which are to be balanced, each pedestal comprising a base body and a vibrating bridge which carries a bearing for the rotor and is mounted on the base body by a pair of vertical leaf springs, said bearings being arranged so as to locate, in use, the rotor with its longitudinal axis offset from and parallel to a plane extending medially with respect to each pair of leaf springs, said machine further including a processing-unit carrier running parallel to said longitudinal axis.

2. A machine as claimed in Claim 1, in which, in use, the longitudinal axis of the rotor is disposed above the base bodies of the pedestals.

3. A machine as claimed in Claim 2, in which, in use, the longitudinal axis of the rotor is disposed substantially above one vertical end surface of each base body.

4. A machine as claimed in Claim 1, in which, in use, the longitudinal axis of the rotor is horizontally offset with respect to each base body.

5. A machine is claimed in any one of Claims 1-4 having a rotor supported by said bearings, the mass of each vibrating bridge is substantially greater than the proportion of the rotor mass supported by the bearing of the bridge.

6. A machine as claimed in any one of Claims 1-5 in which the carrier is movable perpendicularly of said longitudinal axis.

7. A dynamic balancing machine substantially as hereinbefore described with reference to, and as shown in, any one of the embodiments illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. along the carrier 40, 43, and by movement of the carrier 40 in one of the directions indicated by arrow 47 can be brought into the operating position determined by axis 9. In Figure 5 the processing unit comprises a driller 48 which by movement in one of the arrow 47 directions can be brought into the vicinity of the machining plane represented by the axis 9. As already described, for each bearing pedestal a separate transducer 11 or 18 picks up the vibrations of the unbalanced crankshaft 32. Leaf springs disposed parallel to each other as shown in Figures 1 and 2 are yielding in the direction of the transducers, so that the vibrations of the rotor being examined can be picked up, but are rigid in the direction perpendicular thereto. Due to this arrangement, and especially with an elongated rotation body, shown as a driveshaft 32, there occur two critical bending frequencies-one critical bending frequency in the direction of the transducer and one critical frequency in a direction perpendicular thereto. However the transducer can only pick up bending frequencies acting in its direction and use them for display or further processing. The bending resonance frequency perpendicular hereto occurs at a lower rotary speed, but cannot be brought to display.The resulting danger is that at this critical rotary speed the rotor being examined can already undergo damage, without the operative being able to adjust to this. If each of the two vibrating bridges 7 has an appreciably greater mass than the proportionate share of the rotor weight, the critical resonance frequency in the test direction is reduced to a lower rotary speed, and hence also its difference from the lower critical fequency in a direction perpendicular ito the test direction is reduced. This ensures that before the lower critical frequency arises, the higher critical frequencv operating in the test direction already becomes clearly noted, for example through migration of the unbalance display from a previously adopted position, so that the dynamic balancing rotary speed can be limited in good time and prevent damage occurring. Particularly with flat based dynamic balance machines, the vibrating bridge 7 may also be integrated in the base body 1 by making this body U-shaped, and displacing the longitudinal axis of the bearing relative to the base body centre 10, within this U-shape. WHAT WE CLAIM IS:

1. A dynamic balancing machine with bearing pedestals disposed on a machine bed to support rotors which are to be balanced, each pedestal comprising a base body and a vibrating bridge which carries a bearing for the rotor and is mounted on the base body by a pair of vertical leaf springs, said bearings being arranged so as to locate, in use, the rotor with its longitudinal axis offset from and parallel to a plane extending medially with respect to each pair of leaf springs, said machine further including a processing-unit carrier running parallel to said longitudinal axis.