Claims:WE CLAIM:
1. A device to remove annular member from an inner member of large turbogenerator comprising a ring assembly secured to said annular member shrunk fitted on the inner member, wherein a clamp assembly is connected to the ring assembly and secured on the inner member.
2. A device to remove annular member from an inner member of large turbogenerator as claimed in claim 1, wherein the ring assembly is threadedly secured to the annular member by means of fastener.
3. A device to remove annular member from an inner member of large turbogenerator as claimed in claim 1 or 2, wherein the annular member includes a permanent magnetic hub and the inner member includes an exciter rotor shaft.
4. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims, wherein the circular ring is having a plurality of holes therealong at a fixed pitch, outer surface of which is fixedly secured to multitude of lugs spaced at equal circumferential distance thereof.
5. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims, wherein the clamp assembly constitutes two halves or semi-circular portions wherein each portion is secured to a plurality of lugs arranged in circular array on outer surface thereof and is having a clamping lug projected from each end thereof, in which said each clamping lug is provided with a hole at the centre thereof.
6. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims, wherein the lug is having substantially cuboidal block profile with a hole at center thereof.

7. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims, wherein the semicircular portions of said clamping ring assembly, and the ring assembly and clamping ring assembly are fastened to each other by means of multitude of fasteners including bolt, stud, nut, washer.
8. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims, wherein the exciter rotor is provided with a load bearing shoulder for transition of the rotor from one diameter to another diameter.
9. A method of removing annular member from an inner member of large turbogenerator as claimed in any of the preceding claims comprising heating the annular member evenly and externally accommodating said exciter rotor for expansion of said annular member followed by application of pressure to remove the annular member from said inner member such as herein described.
10. A device to remove annular member from an inner member of large turbogenerator as claimed in any of the preceding claims wherein the clamp assembly abuts the rotor shoulder to provide means of axially locating the clamp assembly and to carry the thrust loads during pulling the annular member.
, Description:A device and method to remove annular member from an inner member of large turbogenerator
FIELD OF INVENTION
[001] The present invention relates to a device and method to remove annular member from an inner member of large turbogenerator. The annular member and inner member includes permanent magnet hub and an exciter rotor shaft respectively. The method involves application of heat to enable thermal expansion of the outer member and simultaneously applying sufficient differential axial pressure to force the members apart and at the same time preventing any damage to any of the shrunk fit members.
BACKGROUND OF THE INVENTION

[002] In the event, a new large size generator or one which has been idle for a long period of time is put into operation, generally used in power plants, it is necessary to provide an external voltage source to excite the field coil prior to production of voltage. This is accomplished by a pilot exciter, having permanent magnet material and magnet hub, magnet holding poles, aluminium plates and screw. Exciter rotor is coupled with Turbo generator and in turn the Turbo Generator is coupled with Steam Turbine (prime mover). The entire exciter rotor, turbo generator rotor and turbine rotor train, coupled in line, rotates at 3000 revolutions per minute and pilot exciter generates electromotive force with the help of permanent magnet and armature winding thereof. These permanent magnets are assembled on magnetic hub that is shrinkfitted on exciter rotor shaft.
[003] Accordingly, it has been a conventional practice to secure the permanent magnets to an exciter rotor by a shrinkage fit, a well-known industrial manner of effecting a rigid, nonloosening, fixed connection between metal members wherein an annular member such as a permanent magnetic hub, which is first furnace heated to expand it so that its normally smaller inner diameter enlarges sufficiently to receive an inner member i.e., exciter rotor, freely so that when the annular member cools and the inner diameter returns toward its normal dimension, it will grip the rotor in interference fit or shrinkage fit. Shrinkfit components are more acceptable in high- speed operations because their absolute symmetry of form provides the best possible balance and thereby providing a gripping force greater than any other known method.
[004] However, an especially costly Situation prevails due to the difficulty in replacing any one or more of the members.When a member or plurality of members are mounted in interference fit on a shaft or rotor and become worn or damaged and if replaced or repaired would significantly prolong the useful life of the excitation system.
[005] Separation of shrinkfitted members has been accomplished in various ways, such as by introduction of hydraulic medium to the interference surfaces in order to expand the outer member and to lubricate the surfaces sufficiently to enable sliding the members apart. This requires a ready source of hydraulic pressure, and requires fitting the involved piece of equipment with high pressure connections and porting, often not available or feasible.
[006] Another manner of Separation involves application of sufficient differential axial pressure to force the members apart, but, in absence of a proper fixture, this also usually results in at least one of the members being damaged to the extent that it may have to be scrapped.
[007] Still another method of separating such members requires boring off the inner surface of shaft member thereby destroying it, and subjecting the other member to the hazard of possible irreparable damage.
[008] A further known method of effecting separation includes grossly heating the outer member to the point where its expansion will be greater than the expansion of the inner member from the effects of the heating so as to enable removal of one member from the other.
[009] The permanent magnet hub 4 is maintained at the selected place on the exciter rotor 5 fixedly against at least axial displacement by interference or shrink fit wherein the annular member permanent magnet hub 4 has normal inside diameters slightly smaller than the diameter of the selected area on the exciter rotor 5 on which it is mounted, and such annular member permanent magnet hub 4 is heated to expand the same to enlarge the inside diameters thereof temporarily and sufficiently in order to effect relative axial movement of the same into position on the exciter rotor 5 and upon cooling and shrinking onto the shaft maintaining the shrinkfit.
[0010] Incase the permanent magnet hub 4 gets damaged or worn,which requires replacement or reconditioning, it must be removed from the exciter rotor 5 and replaced either after reconditioning or by a spare permanent magnet hub in order to salvage the assembly for use.
[0011] In view of the above, the present inveniton has been introduced which can address the issues of prior artsand at the same time serve the purpose efficiently.
OBJECTS OF THE INVENTION

[001] An object of the present invention is to provide a device and method to remove annular member from an inner member of large turbogenerator which obviates shortcomings of the prior arts.
[0012] Another object of the present invention is to provide a device and method to remove annular member from an inner member of large turbogenerator which is simple in construction.

[0013] Yet another object of the present invention is to provide a device and method to remove annular member from an inner member of large turbogenerator which is cost effective and consumes less time.

[0014] A further object of the present invention is to provide a device and method to remove annular member from an inner member of large turbogenerator wherein the metallurgical characteristics of the members are preserved against deterioration and may even result in an improvement in such characteristics.

[0015] Yet further object of the present invention is to provide a device and method to remove annular member from an inner member of large turbogenerator enabling economical reconditioning and salvaging of valuable tools.

SUMMARY OF THE INVENTION

[0016] According to the present invention, separation of any selected one or more of the annular members from the exciter rotor 5 is adapted to be accomplished selectively and economically by effecting a temperature differential between the exciter rotor and the annular member, including induction of heat from and expanding the annular or hub member relative to the inner or rotor member, until they are loose from each other, and separating the thus loosened members by applying sufficient differential axial pressure using a deviceto force the members apart and subsequently pulling out the magnetic hub from the exciter rotor and at the same time preventing any damage to any of the member viz. magnet hub or the exciter rotor.
[0017] However, during the removal of shrunk fit members, a peculiar problem which exist is that different materials have different tendency to change in shape, area, and volume in response to a change in temperature i.e., they have different coefficient of thermal expansion. Larger the coefficient, more will be the dimensional changes when subjected to heat. Magnet hub, comparatively, has a lower coefficient of thermal expansion than the metallic exciter rotor however less heat, when applied on annular member from outside, reaches the exciter rotor. Consequently, a temperature gradient must be created between the hub and the rotor but keeping in mind that large degree of heat shall impair the metallurgical properties of the hub. Therefore, as soon as the permanent magnet hub expands, a pressure has to be applied to pull it out from the rotor using a fixture that exerts even, or at least balanced pressure since hammering is not allowed on hub because its pole ribs and holes are prone to deformation and finally getting damaged. Therefore, at the time of heating, it is required to apply sufficient differential balanced axial pressure to force the members apart and at the same time preventing any damage to magnet hub or the exciter rotor.
[0018] According to the present invention, the foregoing and other disadvantages, shortcomings, inefficiencies and problems are overcome by introducing a device and method for separating interference or press-fitted members.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0019] Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which:

Figure 1shows: A sectional view illustrating a device comprisingof ring assembly,clamp assembly and studs in accordance with this invention.
Figure 2 shows: An illustrative view of an examplary permanent magnetic hub-exciter rotor shrunkfit structure on which the device is mounted, according to one embodiment of the present invention.
Figure 3 shows: An exploded view of the proposed device, according to one embodiment of the present invention.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

[0020] The instant invention pertains to a device and method to remove annular member from an inner member of large turbogenerator.

[0021] By way of example of an assembly including at least a pair of members which are in interference or press fit attachment to one another and in respect to which the new method and device of the present invention are especially useful, a permanent magnet hub 4 and an exciter rotor 5 assembly having a co-rotational relationship through a shrinkfit has been selected.

[0022] Referring now to the accompanying figures more in detail, wherein like numerals have been employed to designate similar parts throughout the various figures, it can be seen that one embodiment of the invention includes a device designated generally by the numeral D. Referring to Figure 1, device D, comprises of ring assembly 1, clamp assembly 2 and plurality of studs 3,which is connected to a permanent magnetic hub 4 shrunk on exciter rotor 5. The hub 4 is having plurality of threaded holes 15 arranged in a circulararray on transverse face thereof. The exciter rotor 5 has a load bearing shoulder 5'that transitions the rotor from a first diameter to a second diameter.

[0023] Referring to figure 2 and 3, wherein a ring assembly 1, of device D, comprising of a circular ring 11 having a plurality of holes 12therealong at a fixed pitch and arranged in circular array. The circular ring 11, outer surface of which is fixedly secured to multitude of lugs 13spaced at equal circumferential distance of the ring.

[0024] A clamp assembly 2, of device D, constitutes two halves or semi-circular portions 21, 22 wherein each portion(21, 22) is secured to a plurality of lugs (23,25) arranged in circular array on outer surface thereof. The lug (13, 23) is having substantially cuboidal block profile with a hole (14, 24) at center thereof. Each semi-circular portion(21,22) is also having a clamping lug(25) protruding from each end thereof wherein each clamping lug 25 is having a hole 28 at the centre thereof. A fastener, such as a bolt 26, inserts through hole 28 in clamping lug 25 of semi-circular portion 21and engages the hole 28 in clamping lug 25 of semi-circular portion 22. Bolts 26 have head 31 that have drive surfaces for engagement by a tool, such as a socket of an air impact wrench. Preferably bolts 26 are retained with clamp portion 22 by engaging a nut 27 or retention devices, such as a retainer ring (not shown in figure), such that when detached from the semi-circular portion 21, each bolt 26 is loosely retained with semi-circular portion 22. Alternately, one bolt 26 could be retained with semi-circular portion 21 and the other with semi-circular portion 22.

[0025] Referring to figure 2, each of the pulling studs 3 is having head 32 and threaded shank 33 perpendicularly disposed through the Ring assembly 1 and clamping ring assembly 2.

[0026] The process of pulling the magnet hub out involves heating the metallic permanent magnetic hub 4 evenly from the outside while avoiding too much of heat directly next to the exciter rotor 5 and thereby expanding the permanent magnetic hub 4 by heating it through any of the heating mode, including flame, induction, radiant. The ring assembly 1 and permanent magnetic hub 4, in shrinkfit condition, are assembled together using a fastener, such as a bolt 16, that inserts through hole (12, fig. 3) of circular ring 11 of ring assembly 1 and engages the threaded holes 15 in permanent magnetic hub 4. The clamp assembly 2, constituting assembled semicircular portions 21, 22 is fastened on the exciter rotor 5 by means of fastening means 26, 27 in a way 'äbutting rotor shoulder in order to provide means of axially locating the clamp assembly 2 and to carry the thrust loads generated while pulling the permanent magnetic hub 4 as there would be significant rectilinear movement of the ring assembly 1 relative to and towards the clamp assembly 2 with tightening of the nut 34 on plurality of pulling studs 3 through hole 14. All pulling studs3 have their head 32 abut the lugs 13 on ring assembly 1 end and threaded shank 33 part of each pulling stud 3 is supported by and passes through hole 24 of lug 23 in clamp assembly 2. Rotation of nut (34, fig. 2) causes ring assembly 1, along with permanent magnetic hub 4, to move axially toward each other allowing the permanent magnet hub to move slowly out from the rotor (5). Washer 29, 35 are placed in between nut 27, 34 and lug 25, 23 so asto distribute the pressure of the nut evenly over the lug 23 surface. So that the lug surface isn't damaged, and also to ensure that the nut is pressed against a smooth surface, thereby reducing the chance that it will gradually loosen because it is in contact with an uneven surface.

[0027] Studs 3, of relatively large pitch, provides the ability to obtain much more accurate torque values and do not twist during tightening unlike bolts. The threaded shank 33 surface area also aids to resist axial pull-out forces along with rotor shoulder.

[0028] In Order to prevent damage to rotor surface during the process of pulling out permanent magnetic hub, a rubber sheetis glued on the inner radius of each semi-circular portions 21, 22 through an adhesive having ideal strength properties resulting in Substrate bonding of rubber sheetwhich is maintained over a long period depending on the existing and Chemical environmental factors.

[0029] Although the present discussion imparts teaching regarding a device and means to remove an annular shrunk fit member from an inner shrunk fit member, it will be appreciated that the device and methods discussed may be readily adapted for use with other similar procedures. Not only will the device help in easy removal of shrink fit components but is cheap and easy to manufacture and shall provide safer and ergonomic means for the operators to deal with heated shrunk fit members. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.