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Title:
DRIVE APPARATUS FOR A RAILWAY WHEEL MACHINING DEVICE
Document Type and Number:
WIPO Patent Application WO/2015/066774
Kind Code:
A1
Abstract:
An apparatus for driving a railway wheelset in a wheel machining device. The wheelset including opposing wheels 6,7 rotatable about a longitudinal axis. The apparatus including at least one drive assembly 11 for contacting a sidewall of at least one wheel 6,7 to thereby impart rotational motion to the wheelset, and a positioning mechanism 13 operatively connected to the drive assembly 11 for positioning the drive assembly 11 with respect to the wheel 6,7. In use, as the wheel 6,7 is rotated by the drive assembly 11, the drive assembly 11 is free to move relative to the positioning mechanism 13, in unison with back and forth lateral movement of the wheel's sidewall caused by uneveness in the wheel's sidewall.

Inventors:
TAYLOR, Chris (18 Windsor Drive, Beaconsfield, Victoria 3807, AU)
ELLUL, David (20 Victoria Road, Langwarrin South, Victoria 3911, AU)
BRUGEAUD, Chris (47 Split Rock Road, Upper Beaconsfield, Victoria 3808, AU)
VOGEL, Heinz (Nurtinger Strabe 78, Oberboihingen, 72644, DE)
Application Number:
AU2014/050346
Publication Date:
May 14, 2015
Filing Date:
November 11, 2014
Export Citation:
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Assignee:
MARAND PRECISION ENGINEERING PTY LTD (153 Keys Road, Moorabbin, Victoria 3189, AU)
International Classes:
B23B5/34; B23B5/28
Foreign References:
GB824086A1959-11-25
CZ283438B61998-04-15
DE20020237U12001-04-12
GB849291A1960-09-21
US3345890A1967-10-10
GB1547823A1979-06-27
Attorney, Agent or Firm:
WATERMARK PATENT & TRADE MARKS ATTORNEYS (Level 2/302 Burwood Road, Hawthorn, Victoria 3122, AU)
Download PDF:
Claims:
THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An apparatus for driving a railway wheelset in a wheel machining device, the wheelset including opposing wheels rofatabie about a longitudinal axis, the apparatus including:

at least one drive assembly for contacting a sidewall of at least one of the wheels to thereby impart rotational motion to the wheelset, and

a positioning mechanism operativeiy connected to the drive assembly for positioning the drive assembly with respect to the wheel,

wherein, in use, as the wheel is rotated by the drive assembly, the drive assembly is free to move relative to the positioning mechanism, in unison with back and forth lateral movement of the wheel's sidewall caused by uneveness in the wheel's sidewall.

2. An apparatus as claimed in claim 1 wherein the apparatus further includes a slip control mechanism operativeiy connected to the drive assembly and the wheelset, the slip control mechanism controlling the force by which the drive assembly contacts the wheel to impart rotational motion,

3. An apparatus as claimed in either claim 1 or 2 wherein the drive assembly includes a slide plate, the slide plate being moveably mounted to the positioning mechanism for movement in a direction parallel to the longitudinal axis of the wheelset.

4. An apparatus as claimed in claim 3 wherein the drive assembly further includes a first drive for contacting a first sidewall of the wheel, the first drive being rigidly mounted to the slide plate.

5. An apparatus as claimed in claim 4 wherein the drive assembly further includes a second drive for contacting a second sidewall of the wheel, the second drive being moveably mounted on the slide plate for movement in a direction parallel to the longitudinal axis of the wheelset.

6. An apparatus as claimed in claim 5 wherein the drive assembly further includes an actuator for moving the second drive with respect to the slide pfate in said direction parallel to the longitudinal axis of the wheeiset.

7. An apparatus as claimed in claim 6 wherein the positioning mechanism includes a primary guide rail, the slide plate being mounted on the primary guide rail for sliding movement there along.

8. An apparatus as claimed in claim 7 wherein slide plate includes a secondary guide rail, the second drive being mounted on the secondary guide rail for sliding movement there along.

9. An apparatus as claimed in claim 7 wherein the positioning mechanism further includes a primary stopper for limiting travel of the slide plate and first drive mounted thereto, in an inbound direction towards the opposing wheel of the wheeiset,

10. An apparatus as claimed in claim 9 wherein the positioning mechanism further includes a secondary stopper for limiting travel of the second drive in an outbound direction away from the opposing wheel of the wheeiset.

1 1 . An apparatus as claimed in claim any one of claims 6 - 10 wherein the actuator includes a piston within a main body of the actuator, the main body being mounted to the slide plate, a distal end of the piston being connected to the second drive.

12. An apparatus as claimed in claim 11 wherein retraction of the piston with respect to the main body of the actuator pulls the second drive in the outbound direction away from the second sidewall of the wheel until the second drive abuts with the secondary stopper.

13. An apparatus as claimed in claim 12 wherein retraction of the piston with respect to the main body of the actuator moves the first drive in the inbound direction away from the first sidewail of the wheel when the second drive abuts the secondary stopper.

14. An apparatus as claimed in any one of claims 11 - 13 wherein extension of the piston with respect to the main body of the actuator pushes the second drive in the inbound direction until the second drive abuts with the second sidewail of the wheel.

15. An apparatus as claimed in any one of claims 11-14 wherein extension of the piston with respect to the main body of the actuator moves the first drive in the outbound direction towards the first sidewail of the wheel when the second drive abuts the second sidewail of the wheel.

16. An apparatus as claimed in either claim 4 or 5 wherein the first drive includes a first roller for contacting the first sidewail of the wheel and the second drive includes a second roiier for contacting the second sidewail of the wheel, the roliers being rotatable about an axis substantially perpendicular to the longitudinal axis of the wheelset.

17. A wheel machining device for machining a railway wheelset having opposed wheels rotatable about a longitudinal axis, each wheel having a wheel running surface, the device including an apparatus as claimed in any one of claims 1 to 16 for driving the wheelset, the device further including at least one roller assembly for supporting the wheelset, the roller assembly including at least one support roller for engaging with the wheel running surface of a wheel.

18. A wheel machining device as claimed in claim 17 wherein the at least one support roller includes a cambered surface, wherein in use, as the wheel running surface is being machined to form a new running surface, the cambered surface of the support roller smoothly transitions over to the new running surface.

19. A wheel machining device as claimed In claim 18 further including an axle centring chuck for engaging with opposing ends of the wheelset.

Description:
DRIVE APPARATUS FOR A RAILWAY WHEEL MACHINING DEVICE

FIELD OF THE INVENTION

[00013 The present invention relates to a drive apparatus for a railway wheel machining device. More particularly, the present invention relates to an apparatus for driving a railway wheelset in a wheel machining device and a wheel machining device incorporating such an apparatus, for example, an above floor wheel lathe, an under floor wheel lathe, a portal wheel lathe or any other type of wheel machining device for the profiling of railway wheels.

BACKGROUND TO THE INVENTION

[OOO23 The wheels and associated brake discs of trains, locomotives and other forms of railway vehicles are subjected to wear and tear, in order to maintain the wheels, re-profiling of the wheel's running surface is routinely performed with some form of wheel machining device such as a lathe, milling or grinding machine. Likewise, the wheel's associated brake discs require re- profiiing at times to maintain optimum performance.

[0003] In order to profile a wheel running surface, the railway wheelset requires some form of clamping arrangement and associated drive means in order to facilitate rotation of the wheels for the profiling process,

[0004] On some machines, rotation of the wheels is provided by radial clamping. In this respect, rotation of the wheels is provided by a series of radially positioned motorised drive rollers which contact the wheel running surface, ie the surface requiring profiling. During profiling, a cutter moves across the wheel running surface which creates a step in the running surface as it cuts to create a new wheel running surface. As the drive rollers are engaged with the wheel running surface, the drive rollers are in contact with the step. In order for the drive rollers to transition smoothly down the step onto the newly created wheel running surface with minima! drive power loss to the wheel, the drive rollers are provided with a camber. However, as there is a limit to the amount of camber that can be provided on the drive rollers, there is a limit to the depth of cut which the rollers can successfully negotiate without abruptly falling off the step onto the new running surface. Accordingly, the cutting depth during profiling must be restricted. In addition to this problem, there may be flat spots on the wheel running surface caused by wheel skidding during an in-use braking procedure, which during re-machining causes an uneven running surface for the drive rollers contacting on the wheel running surface.

[0005J On other machines, rotation of the wheels is provided by axial clamping. In this respect, rotation of the wheels is provided by a series of axial ly extending rod members having ends which press against a side of the wheel. The rod members are associated with a drive spindie which rotates to drive the wheel. Axial thrust generated in the wheel is reacted against a large thrust bearing inside of the drive spindle. The problem with machines utilising this form of axial clamping is that thrust bearings have a finite life and therefore require replacement at times. Further, thrust bearings are expensive and have very stringent installation specifications in order to perform optimally.

[00063 ln addition, the ends of the rod members may have serrations to reduce the amount of pressure which must be exerted on the wheel to prevent slippage and drive rotation. However, the serrations can cause coarse indentation marks on the wheel which can result in the initiation of cracks and corrosion. Excessive pressure exerted on the wheel by the rod members can also cause the wheel to deform.

[0007] In light of the above, it would be desirable to provide an apparatus for driving a railway wheelset in a wheel machining device which overcomes or alleviates at least one of the abovementioned problems with the prior art. it would also be desirable to provide a wheel machining device which incorporates such an apparatus. [0008] Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention, ft should not be taken as an admission that any of the materia! formed part of the prior art base or the common general knowledge in the relevant art in Australia or any other country on or before the priority date of the claims herein.

SUMMARY OF THE INVENTION

[0009] In accordance with the present invention, there is provided an apparatus for driving a railway wheelset in a wheel machining device, the wheelset including opposing wheels rotatable about a longitudinal axis, the apparatus including:

at least one drive assembly for contacting a sidewail of at least one of the wheels to thereby impart rotational motion to the wheelset, and

a positioning mechanism operativeiy connected to the drive assembly for positioning the drive assembly with respect to the wheel,

wherein, in use, as the wheel is rotated by the drive assembly, the drive assembly is free to move relative to the positioning mechanism, in unison with back and forth lateral movement of the wheel's sidewail caused by unevenness in the wheel's sidewail.

[0010] The apparatus may further include a slip control mechanism operativeiy connected to the drive assembly and the wheelset. The slip control mechanism controls the- f notional driving force by which the drive assembly contacts the wheel to impart rotation or motion sufficient for the machining of the running surfaces. In this regard the slip control mechanism is preferably able to prevent slipping of the drive assembly with respect to the wheel. The slip control mechanism is also preferably able to ensure that the contact force applied to the wheel is substantially no greater than that required to impart rotational motion to the wheel with no slippage during the cutting operations. This advantageously minimises wear and damage to load bearing components and prevents damage to the wheel. [00113 The drive assembl preferably includes a slide plate movabty mounted to the positioning mechanism for movement in a direction parallel to the longitudinal axis of the wheeiset.

[0012] The drive assembly may further include a first drive for contacting a first side wall of the wheel. Preferably, the first drive is rigidly mounted to the slide plate. The drive assembly may further include a second drive for contacting a second side wall of the wheel. Preferably, the second drive is mavably mounted on the side plate for movement in the direction parallel to the longitudinal axis of the wheeiset.

[0013] The drive assembly may further include an actuator for moving the second drive with respect to the slide plate in a direction parallel to the longitudinal axis of the wheeiset.

[0014] The positioning mechanism preferably includes a primary guide rail. The slide plate being preferably mounted on the primary guide rail for sliding movement there along.

[0015j The slide plate preferably includes a secondary guide rail. In this regard, the second drive is preferably mounted on the second guide rail for sliding movement there along.

[0016] The positioning mechanism may further include a primary stopper for limiting travel of the slide plate and the first drive mounted thereto in an inbound direction towards the opposing wheel of the wheeiset

[0017] The positioning mechanism may f urthe include a secondary stopper for limiting travel of the second drive in an outbound direction away from the opposing wheel of the wheeiset. [0018] The actuator ma include a piston within a main body of the actuator. In this regard, the main body may be mounted to the slide plate with a distal end of the piston being connected to the second drive. Preferably, retraction of the piston with respect to the main body of the actuator pulls the second drive in the outbound direction away from the second side wall of the wheel until the second drive abuts with the secondary stopper of the positioning mechanism. In addition, when the second drive abuts the secondary stopper, further retraction of the piston wit respect to the main body of the actuator preferably moves the first drive in the inbound direction away from the first side wall of the wheel.

[0019] In contrast, extension of the piston with respect to the main body of the actuator preferabl pushes the second drive in the inbound direction until the second drive abuts with the second side wall of the wheel. When the second drive abuts the second side wall of the wheel, further extension of the piston with respect to the main body of the actuator preferably moves the first drive in the outbound direction towards the first side wall of the wheel.

[0020] The first drive preferably includes a first roller for contacting the first side wall of the wheel and the second drive preferably includes a second roller for contacting the second side wall of the wheel. The rollers are preferably rotatabie about an axis substantially perpendicular to the longitudinal axis of the wheelset and tangent at the contact point between the wheelset and the drive roller.

[0021] In a further aspect of the invention, there is provided a wheel machining device for machining a railway wheelset having opposed wheels rotatabie about a longitudinal axis, each wheel having a wheel running surface. The wheel machining device includes an apparatus as described in the first aspect of the invention for driving the wheelset. The device further includes at least one roller assembly for supporting the wheelset. The roller assembly including at least one support roller for engaging with the wheel running surface of a wheel. [0022] At least one support roller of the wheel machining device preferably includes a cambered surface, wherein in use, as the wheel running surface is machined to form a new running surface, the cambered surface of the support roller smoothly transitions over to the new running surf ace.

[0023] The wheel machining device may further include an axle centering chuck for engaging and supporting opposing ends of the wheelset.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further benefits and advantages of the present invention wilf become apparent from the following description of preferred embodiments of the invention. The following description should not be considered as limiting any of the statements in the previous section. Preferred embodiments will be described with reference to the following figures in which:

[0025] Figure 1 is a perspective view of a wheel machining device in the form of a portal wheel lathe which incorporates an apparatus for driving a railway wheelset, the apparatus having a pair of drive assemblies in accordance with an embodiment of the invention;

[0026] Figure 2 is a front view of the portal wheel lathe illustrated in Figure t , showing a railway wheelset positioned in the lathe;

[0027] Figure 3 is a side view of the portal wheel lathe illustrated in Figure 1 , showing the railway wheelset positioned in the lathe;

(00283 Figure 4 is a vertical sectional view of the lathe and wheelset through the line B-B in Figure 3; [0029] Figure 5 is a side view of the lathe illustrated in Figure 2 through the line A-A showing the support roller assembly of the lathe in a tilted position to stop the wheelset after entering the iathe,

[0030] Figure 6 is a side view of the lathe illustrated in Figure 1 showing the wheelset lifted into position by the support roller assembly;

[0031 ] Figure 7A is a perspective view of an inboard drive (a first drive) of a drive assembly in the lathe illustrated in Figure 1 ;

[0032] Figure 7B is a perspective view of an outboard drive (a second drive) of a drive assembly in the lathe illustrated in Figure 1 ;

[0033] Figure 8 is a perspective view of the positioning mechanism of the apparatus with a pair of drive assemblies mounted to the positioning meehanism, the inboard drive of each drive assembly being in a maximum inbound position and the outboard drive of each drive assembly being in a maximum outbound position.

[0034] Figure 9 is a perspective view of the positioning mechanism and pair of drive assemblies shown in Figure 8. with the inboard and outboard drives of each drive assembly being in contact with the wheels of the railway wheelset.

[0035] Figure 10A is a perspective view of the positioning mechanism shown in Figure 8 with the drive assemblies removed to show various components of the positioning mechanism;

[0036] Figure 1 QB is a perspective view of the positioning meehanism shown in Figure 8 with various components of the drive assemblies removed to show each drive assemblies slide plate attached to a corresponding primary guide rail of the positioning mechanism; [0037] Figures 1 1 A to 11 F illustrate the operational sequence of the drive assemblies when engaging the railway wheelset;

[0038J Figure 12A illustrates a cutter of the !athe illustrated in Figure 1 , profiling the wheel running surface of a wheel of the wheelset;

[00393 Figures 12B and 12C illustrate a support roller of a roller assembly of the wheel machining device illustrated in Figure 1 , engaging with the wheel running surface of heel being machined;

[0040] Figure 13A illustrates an embodiment where the drive assembly includes a first drive having a motor associated with one wheel and a second drive having a motor associated with the other wheel;

[0041 ] Figure 13B illustrates an embodiment where the drive assembly includes a first drive having a motor on one side of the wheel and a second drive having a motor on the other side of the same wheel;

[00423 Figure 13C illustrates an embodiment where a pair of drive assemblies are provided with only one drive of each assembly having a motor; and

[00433 Figure 13D illustrates a preferred embodiment where a pair of drive assemblies are provided with each drive having a motor.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0044] For convenience, the invention will be described in relation to a wheel machining device in the form of a portal wheel lathe, it should however b understood that the invention is equally suitabie for use with other forms of wheel machining devices. [0045] With reference to Figures 1 to 6 of the accompanying drawings there is shown a wheel machining device in the form of a portal wheel lathe 1 for machining a railway wheeiset 5. The wheeiset 5 preferably includes a first wheel 6 and an opposing second wheel 7, The wheels 6, 7 are interconnected by an axle 9 having a longitudinal axis about which the wheels 6, 7 are rotatable. The lathe 1 incorporates an apparatus 3 for driving the railway wheeiset 5 in the lathe 1 during machining of the wheels 6, 7 and associated brake discs of the wheeiset 5.

[0046] The apparatus 3 for driving the railway wheeiset 5 includes at least one drive assembly 1 1 for imparting rotational motion to the wheeiset 5. In the preferred embodiment illustrated in Figures 8 and 9, two drive assemblies are provided with a first drive assembly 11 being provided for the first wheel 6 and a second drive assembly 12 being provided for second wheel 7. It should however be appreciated that in other embodiments of the invention only one wheel 6 of the wheeiset 5 may have a drive assembly 1 1 , or a single drive assembly ma straddle both wheels 6, 7, as illustrated in Figure 13A.

[0047] The apparatus i further includes a positioning mechanism 13. In the embodiment illustrated in Figures 8 and 9, the positioning mechanism 13 is operatively connected to the pair of drive assemblies 11 , 12 for positioning the drive assemblies 1 1 , 12 with respect to the wheeiset 5. As the operation and components of the drive assemblies 11 , 12 are identical, it will be convenient to describe operation of only the first drive assembly 1 1 with reference to the first wheel 6. The first drive assembly 11 functions to contact a sidewall of the first wheel 6 to thereby impart rotational motion to the wheeiset 5. In use, as the first wheel 6 is rotated by the first drive assembly 11 , the first drive assembl 11 is free to move relative to the positioning mechanism 13, in unison with back and forth lateral movement of the first wheel's sidewall caused by unevenness in the wheel's side wall. [0048] The first drive assembly 11 preferably includes a slide plate 15 moveab!y mounted to the positioning mechanism 13 for movement in a direction parallel to the longitudinal axis of the wheefset 5.

[0049] The first drive assembly 11 further includes a first drive 16 for contacting a first side wall 18 of the first wheel 8. The first drive 16 is rigidly mounted to the slid plate 15. As the first drive 16 is positioned to an inner side of the first wheel 6 it is regarded as the inboard drive 16,

[0050] The first drive assembly 11 further includes a second drive 20 for contacting a second side wail 22 of the first wheel 6. The second drive 20 is moveabiy mounted on the slide plate 15 for movement in a direction parallel to the longitudinal axis of the wheelset 5. As the second drive 20 is positioned to the outer side of the first wheel 6, the second drive 20 is regarded as the outboard drive.

[0051 ] The first drive assembly 1 1 further includes an actuato 24 for moving the outboard drive 20 with respect to the slide plate 15 in a direction parallel to the longitudinal axis of the wheelset 5. The actuator 24 is preferably in the form of a servo actuator.

[0052] With reference to Figures 10A and 10B, the positioning mechanism 13 includes a primary guide rail 26 to which the slide plate 15 is mounted for sliding movement there along. In Figure 10B 5 the slide plate 15 is shown mounted to the primary guide rail 26. The slide pfate 15 includes a secondary guide rail 28 to which the outboard drive 20 is mounted. The outboard drive 20 being able to slide along the secondary guide rail 28. The positioning mechanism 13 further includes a primary stopper 30 positioned at one end of the primary guide rail 26. The primary stopper 30 f unctions to limit travel of the slide plate 15 and the inboard drive 16 mounted thereto, in an inbound direction towards the opposing wheel 7 of the wheelset 5. The positioning mechanism 13 further includes a secondary stopper 32 for limiting travel of the outboard drive 20 in an outbound direction away from the opposing wheei 7 of the whee!set 5. The secondary stopper 32 preferably projects in a direction perpendicular to the primary stopper 30 and the primary guide rail 26.

[0053] The actuator 24 may include a piston 34 within a main body 36 of the actuator 24. The main body 36 is secured to the slide plate 15 and a distal end of the piston 34 which projects from the main body 36 is connected to the outboard drive 20. The actuator 24 may however be of any other weii known form, for example the actuator 24 could be in the form of a screw and nut driven by an electric motor.

[0054] The inboard drive 16 includes a first roller 17 for contacting the first sidewail 18 of the first wheel 6 and the outboard drive 20 includes a second roller 21 for contacting the second sidewail 22 of the first wheel 6. The first and second rollers 17, 21 are preferably rotatable about an axis substantially perpendicular to the longitudinal axis of the wheelset 5. The rollers 17, 21 contact angle may however be adjusted for the wheel size to allow superior contact between the rollers 17, 21 and the wheel 6.

[0055] With reference to Figure 7A, the first roller 17 of the inboard drive 16 includes a replaceable roller tyre 19. Likewise, with reference to Figure 7B, the second roller 21 of the outboard drive 20 includes a replaceable roller tyre 23. Further, at least one of the two drives 16, 20 preferably includes a servo motor 25 and associated gearbox at one end. As shown in Figure 7B S the outboard drive 20 includes a secondar slide table 27 for enabling the outboard drive 20 to slide along the secondary guide rail 28 of the slide plate 15. in contrast, the inboard drive 16 includes a block 29 for rigid mounting of the inboard drive 16 to the slide plate 15, as shown in Figure 7A,

[0056] In Figure 8, the slide plate 15 of both drive assemblies 11 , 12 are in a maximum inbound position whereby the slide plate 15 is in abutment with the primary stopper 30 of the positioning mechanism 13. In this position the inboard drives 16 are spaced a maximum distance from the wheels 6. 7. The secondary slide table 27 of the outboard drive 20 is in abutment with the secondary stopper 32. Accordingly, the outboard drives 20 are spaced a maximum distance from the wheels 6, 7. In this position there is a gap between the drives 16, 20 for the wheels 6, 7. In contrast, in Figure 9, the inboard drives 16 and the outboard drives 20 are in abutment with the wheels 6, 7.

[0057] The operating sequence of the first drive assembly 11 with respect to the first wheel 6 will be described with reference to Figures 1 1 A to 1 1 F. In the initialisation procedure, the inboard drive 16 and the outboard drive 20 of the first drive assembly 1 1 are force away from each other to open a gap between which the first wheel 6 of the railway wheeiset 5 may fit. The outboard drive 20 is pulled in the outbound direction away from the second side wall 22 by retraction of the piston 34 into the main body 36 of the actuator 24 until the outboard drive 20 contacts the secondary stopper 32, as shown in Figure 1 1 B. As the outboard drive 20 is in abutment with the secondary stopper 32, further retraction of the piston 34 into the main body 36 of the actuator 24 results in the inboard drive 16 being pushed in the inbound direction until the inboard drive 16 is in abutment with the primary stopper 30, as shown in Figure 1 1 C. At this point, both the inboard drive 16 and outboard drive 20 are at their extreme outward positions and the gap between the drives 16, 20 is at a maximum.

[0058] With reference to Figures 1 and 1 1 D, the positioning mechanism 13 is then brought forward and downward using an associated actuator 38 to align the inboard drive 16 and outboard drive 20 with the first wheel 6. With reference to Figure 1 1 E, the outboard drive 20 is then forced inwards towards the first wheel 6 by extension of the piston 34 from the main body 36 of the actuator 24 until the second roller 21 of the outboard drive 20 touches the second side wall 22 of the first wheel 6 near the wheel's running surface. Once this occurs, further extension of the piston causes the inboard drive 16 to be pulled in the outbound direction by the actuator 24 until the first roller 17 of the inboard drive 16 contacts the first side wail 18 of the first whee! 6 near the wheel's running surface, as shown in Figure 11 F. The actuator 24 then increases the contact force exerted by the inboard drive 16 and outboard drive 20 on the first wheel 6 until the drives 16, 18 ciarnp onto the first wheel 6 with the precise force required to drive the first wheel 6 with friction. In this regard, the friction is enough to prevent slippage happening between the drive rollers 1 , 21 of the drives 16, 20 and the first wheel 6 during a cutting operation.

[0059] A slip control mechanism operatively connected to the first drive assembly 1 1 includes a sensor which determines the sfippage and a controller associated with the slip control mechanism uses the slippage information to control the contact pressure between the inboard drive 16 and outboard drive 20 and the first wheel 6 so that the margin for slippage is always in a safe zone. The contact pressure between the drives 16, 20 and the first wheel 8 is preferably kept as low as possible to improve the wear life of the components in contact,

[0060] When the inboard drive 16 and outboard drive 20 of the first drive assembly 11 are in full contact and at the correct contact pressure against the first wheel 6, the motor 25 of the inboard drive 16 and the outboard drive 20 may share the drive power, torque and speed equally, based on one motor being the master and the other motors being in a slave mode, following the power of the master motor. Further, once the inboard drive 16 and out&oard drive 20 are in contact with the first wheel 6, the slide plate 15 is free to float on the primary guide rail 26 in unison with back and forth lateral movement of the side walls 18, 22 of the first wheel 6. This feature is particularly advantageous as the wheel 6 may have unevenness in the wheel's sidewalls 18. 22, where the drives 16, 20 contact the wheel 6. In most cases, the unevenness is due to warpage of the wheel 6, ie the wheel 6 wobbles laterally back and forth when rotated about the longitudinal axis. Unevenness in the wheel's sidewalls 18, 22 can also be due to a variation in the thickness of the wheel 6, ie a variation in the distance between the opposing sidewalls 18, 22 of the wheel 6. With a variation in thickness, the distance between opposing side wails 18, 22 of the wheel 6 ma differ marginall as the wheel 6 is rotated about the longitudinal axis. The floating ability of the slide plate 15 ensures that any warp in the wheel or variation in wheel thickness (at the point where the inboard and outboard drives contact the wheel) is accommodated with the inboard drive 16 and the outboard drive 20 being free to follow in unison the warp or wall thickness variation.

[0061] With reference to Figures 1 to 6, the lathe 1 includes a through port 40 through which the wheelset 5 is positioned for machining. The lathe 1 may further include machine cutters 52, and a pair of roller assemblies 42 for supporting the wheels 6, 7 of the wheelset 5 primarily during the loading process. Each roller assembly 42 may include at least one support roller 44 for engaging with a wheel running surface of the wheel 6, 7. The support rollers 44 may be powered. The lathe 1 further includes a servo actuated axle centering chuck 46 which is engageable with opposite ends of the wheelset axle 9. The centering chuck 48 functions to steady and support the wheelset axle 9 during profiling. Each roller assembly 42 is also operatively connected to a vertical slide 48 which enables the roller assemblies 42 to move upwardly such that the opposing ends of the wheelset axle 9 can engage with the axle centering chuck 46. With reference to Figure 5, the machining process commences with the wheelset 5 being rolled into the lathe 1 along rails 50 which pass through the port 40. As the wheelset 5 passes into the through port 40 the pair of support roller assemblies 42 tilt to stop the wheels 6, 7. The pair of support roller assemblies 42 then return to a horizontal position and lift the wheelset 5 upwardly to an appropriate height for the opposing ends of the wheelset axle 9 to be engaged by the axle centering chuck 46, as shown in Figure 4. The centering chucks 46 advance and hold the wheelset 5 steady on its longitudinal axis. The positioning mechanism 13 then moves forwardly and downwardly such that the inboard and outboard drives 16, 20 are positioned around the wheels 6, 7, The inboard and outboard drives 16, 20 then clamp the wheels 6, 7. A distance sensor makes an accurate scan of the wheel's profile around the full circumference and sends the information to a processor for calculating the correct depth of cut required. The cutters 52 are then lowered and the profiling process commenced, as shown in Figure 6. At the end of the profiling process, the distance sensors make an accurate scan of the wheel's profile around the full circumference and sends the information to a processor for quality analysis. Profiling of the brake discs 54 of the wheelset 5 can also be undertaking in the same manner as the wheels, if required.

[0062J With reference to Figure 12A, a cutter 52 of the lathe 1 is shown profiling the wheel running surface of a wheel 8. As the cutter 52 moves across the wheel running surface, a step is caused in the wheel surface by the cutter 52. With reference to Figures 12B and 12C, the support roller 44 of the roller assembly 42 rests on the wheel running surface as the wheel 6 undergoes profiling by the cutter 52. In this respect, the support rollers 44 assist to absorb vibrations during the cutting process and may vary the force applied to the wheels 6, 7 if necessary. As the cutter 52 advances across the wheel running surface, the support roller 44 remains in contact with the wheel 64 and steps into the newly cut wheel running surface without falling off the step created by the cut. In this respect, the camber on the running face of the support roller 44 has sufficient curvature to cause the crown of the camber to touch the valley of the newly cut wheel running surface while the outside of the camber still runs on the edge where the cutter 52 has just cut, as shown in Figure 12C. As a result, the support roller 44 is able to transition the stepped region smoothly without introducing a sudden jerk.

[00633 Although it is preferable for the apparatus 1 to include a pair of drive assemblies 1 1 , 12 with each inboard drive 16 and outboard drive 20 having a motorised roller, as illustrated in Figure 13D, other arrangements of the drive assemblies 1 1 , 12 are possible with the preferred option and number of drives being dependent upon the power transmission requirements. For example, in the embodiment illustrated in Figure 13A, the apparatus 1 includes a single drive assembly with a first drive 16 being associated with the first wheel 6 and a second drive 20 of the same drive assembly being associated with the second wheel 7. In this embodiment, both drives 16, 20 are motorised. In the

embodiment illustrated in Figure 13B, a single drive assembly 12 is provided with the drive assembly 12 including an inboard drive 16 and an outboard drive 20 which act on opposite sides of the one wheel. In an alternative arrangement, as shown in Figure 13C, the apparatus 1 may include a pair of drive assemblies 1 1, 12 with only the outboard drives 20 of each drive assembly having a motor. The inboard drives 16 in this embodiment may be an idler which reacts to the force imparted on the wheel by the outboard drive 20.

[0064] As the present invention may be embodied in several forms without departing from the essential characteristics of the invention, it should be understood that the above described embodiment should not be considered to limit the present invention but rather should be construed broadly within the spirit and scope of the invention. Various modifications and equivaient arrangements are intended to be included within the spirit and scope of the invention.