AU692882B2 - Improved drive mechanisms - Google Patents

Description

IMPROVEMENTS TO DRIVE MECHANISMS This invention relates to improvements to ride-on mowers incorporating reversible belt drive mechanisms.

Ride-on mowers often utilize reversible belt driven assemblies which transfer drive in the forward and reverse direction through a step down chain drive to the mower's rear transverse drive axle. The drive is actuated by a rocking type pedal in which heel pressure is used to engage reverse drive and toe pressure is used to engage forward drive. For simplicity, light weight and ease of construction, ride-on mowers mostly utilise a transverse drive axle having respective wheel hubs fixed thereto at opposite ends thereof and intermediate spaced chassis mountings which are normally in the form of flangette bearings supporting the transverse axle for rotation. The transverse axle is directly chain driven to a 15 sprocket mounted rigidly on the axle for rotating the driving wheels in unison.

As the width of such mowers is increased for added stability and better traction through wider wheels, the disadvantages of poor steering control inherent in such drive 20 systems becomes more noticeable. Such disadvantages can be overcome to a large extent by the provision of a differential in the drive train to the rear wheels. Unfortunately the differentials available to date have not suited the simple drive trains which utilise a common driving axle as used in most mowers and additionally the available differentials have not had the ability 4-o be selectively utilised or locked in a convenient manner.

The lack of a differential lock is particularly disadvantageous when a ride-on mower is operating on undulating or slippery surfaces as drive can be lost through the differential to a free spinning drive wheel.

While differentials and internal locks therefore are well known, such as is described in US Patent Nos. 3,339,662 and 4,043,224 they are not convenient to use and they are relatively expensive to manufacture.

The chain driven differential illustrated in US patent No.

4,388,842 utilises separate drive axles connected to the respective differentially rotatable sun gears and extending independently from opposite sides of the differential housing, thus requiring long and robust extension housings to support the respective independent drive axles. Accordingly they are not suited for location outwardly of the chassis supports for coupling to the correspondingly located drive sprocket of the final chain drive.

Furthermore the housings for this type of differential have to be made exceedingly robust if they are to cope with the high .loadings applied through such drives without misalignment of the respective drive shafts being induced through the applied 15 loads and leading to premature failure.

The locking mechanisms proposed in the abovementioned patent specifications and conventional differential locking mechanisms are not satisfactory for use with ride-on mowers.

For example, in the internal differential lock illustrated 20 in US Patent No. 4,388,842 partial engagement or disengagement of the locking gear, performed by rotating an externally accessible housing mounted stud with a screwdriver to effect unseen internal adjustment of the locking gear, could cause significant damage to the partially engaged differential gears upon application of a high load thereto, such as can be applied with sudden changes between forward and reverse operation.

These changes in direction are made frequently when mowing with the aforementioned rocking pedal type reversible drive assemblies. Should damage occur it would be internal to the differential housing and repair would not be simple and would be expensive.

Many ride-on mowers are operated in areas where operating conditions vary widely, ranging from well kept turfed areas near dwellings and the like to coarse cut grassed areas around trees and rough areas. Often these areas are mown in a single R~t/0" operation where it becomes necessary to quickly change between full differential operation and locked differential operation.

For example it may be unacceptable to operate with a locked differential on well kept lawn areas as the locked wheels would damage the lawn where sharp turns were negotiated. Then again operating without a locked differential on a slope or slippery area may result in a complete loss of drive. Loss of drive would necessitate dismounting and pushing the mower out of difficulty or locking the differential before driving the mower out of difficulty.

If the differential locking operation is not convenient operators may elect to push the mower. This is an extremely "dangerous operation due to the size of such machines and the proximity of the grass cutting blades. Similar danger may be S 15 apparent if the act of locking the differential necessitates the operator positioning themself directly behind the mower to louk the differential as the mower may accidentally roll backwards over them. Such positioning to effect locking would be the case with the locking mechanism illustrated in US Patent 20 No. 4,388,842.

•o At the very least, gaining access to a differential lock mounted on the chain driven differential housing would be extremely inconvenient due to its position and, as a result of its normal use, its covering with chain grease, soil and grass clippings.

A turf aerating machine manufactured by OMC in the USA described as the OMC GREENSAIRE Mk. II incorporated a chain driven differential supported outwardly of simple axle bearing blocks at opposite sides of the vehicle chassis which support a continuous exposed transverse axle, much in the manner as described above in relation to ride-on mowers. In this differential a tubular chain driven differential housing which carries the planetary gears is mounted rotatably on the transverse axle by a central spider supported boss. This housing is open at one end in order to transmit drive from the

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4 near one of the pair of differentially driven sun gears to the adjacent wheel hub. This near sun gear is supported rotatably on the transverse axle and the other sun gear is fixed to the transverse axle. The adjacent wheel hub which is locked for rotation with the near one of the sun gears effects an operative, but relatively rotatable, closure of the open ended housing.

A resilient peripheral seal is used to close the peripheral gap between the adjacent wheel hub and the open end of the differential housing. This seal is needed for retaining the lubricant which must of necessity be contained in geared differentials and for keeping water, dust and other particulate material away from the meshing gears and central bearing of the supporting boss.

15 A major disadvantage of this arrangement results from the olo fact that loads experienced during working of the machine and which are applied directly to the wheel and its supporting hub V can be transferred to the supporting chassis only by the supported transverse axle.

Inevitably there is deflection of the transverse axle and between the differential parts and the adjacent wheel hub supported thereby. This deflection manifests in misalignment between the differential housing and the wheel hub and thus inefficient working of the peripheral seal.

Furthermore, at rest this static deflection causes a separation between the lower open edge of the differential housing and the adjacent wheel hub and thus the maintenance of a seal in this lower zone is more difficult and is ineffective when worn. High operating loads will result in cyclic reversal of loads applied to the seal and increase wear rates. This could lead to the lubricant leaking from the housing during storage of the apparatus with consequent failure during subsequent use and resultant damage to any grassed areas on which the machine is operated. Of course any such leaking of lubricant onto any grassed areas could not be tolerated.

I RA4-- C 3~ R LU T O Furthermore failure of the peripheral seal also permits particulate material to enter into the housing and cause premature wear.

While it may be possible to make all the components of such a differentially driven transverse axle sufficiently robust to accommodate these wear factors the resultant assembly would be very heavy and expensive to produce. Such a differential would have a large flywheel effect and would place extreme loads on the rest of the drive train during rapid change from forward to reverse drive.

The present invention aims to provide a ride-on mower including a reversible chain drive to a differentially driven rear drive axle assembly which is operable in harsh operating environments safely, reliably and efficiently and which may S 15 also be operated without leaking of lubricant from the .differential and consequent damage to the differential and or grassed surfaces onto which lubricant may leak.

In a further aspect this invention aims to provide a ridemower including a reversible chain drive to a differentially •20 driven rear drive axle assembly which can be selectively locked and unlocked in a convenient and safe manner remote from the differential assembly and/or chain and belt drive assemblies incorporated in the ride-on mower as well as the cutting blades.

With the foregoing in view, this invention resides broadly in a ride-on mower including a chain driven reversible rear drive axle assembly of the type wherein: a differential gear case is mounted rotatably on and supported by a transverse axle which supports respective wheel hubs at opposite ends thereof and which is supported for rotation by spaced chassis mountings intermediate said wheel hubs and through which spaced chassis mountings the transverse axle is attached to the mower's chassis; the gear case is mounted on the transverse axle between one wheel hub and the adjacent chassis support and said one wheel hub is rotatable about the transverse axle; a driven

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<'VT 0 sprocket for the chain drive is attached to the gear case for driving the reversible rear drive axle assembly; the gear case includes a housing which extends co-axially of the transverse axle and which housing carries a pair of opposed planetary gears therein for orbital motion about the transverse axle; opposed sun gears are supported in axially spaced relationship on the transverse arle adjacent said one wheel hub and are differentially driven by the opposed planetary gears; the sun gear nearest said one wheel hub is rotatable about the transverse axle and is drivingly connected to said one wheel hub, and the other sun gear and the other wheel hub are locked for rotation with the transverse axle, and characterised in that:the gear case includes fixed end walls at the opposite ends thereof which enclose the sun gears and planetary gears within the housing; the sun gear nearest said one wheel hub is drivingly connected to said one wheel hub by a tubular portion which passes rotatably through the fixed end wall interposed between said one wheel hub and the sun gear nearest said one wheel hub, and o r the transverse axle passes rotatably through the other end wall and said tubular portion.

This arrangement provides a chain driven reversible rear drive axle assembly having an enclosing gear case which is independent of the adjacent wheel hub and thus alleviates the lubricant leakage and/or peripheral seal disadvantages associated with the OMC chain driven differential.

Preferably there is provided selectively operable differential locking means operable and disposed externally of the gear case and at the side of said one wheel hub which is remote from the gear case for effecting locking of the gear case assembly for rotation with said transverse axle and with said one wheel hub, whereby the respective wheel hubs are locked for rotation in unison with both said transverse axle 7p I3 RA4/ ~jA23 P0 -O 3 ehSC, P4ro and said gear case.

This arrangement provides a lockable chain driven reversible rear drive axle assembly which may be selectively locked and unlocked from a convenient and safe position at the side of the mower and in respect of which the locking means is carried by the wheel hub and thus alleviates the aforementioned disadvantages associated with the earlier locking arrangements.

The differential may be locked in known manner by locking together any of the components which can otherwise rotate differentially, such as by locking means engageable between the sun gear associated with one driven wheel with the gear case or planetary gears. Preferably the selectively operable differential locking means may be manually displaced between an engaged position at which the differential action is prevented 15 and disengaged position at which the differential action ,*.,;operates freely.

More preferably the differential locking means includes an offset locking member which is supported by and extends from said one wheel hub offset from said transverse axle and a locking plate supported slidably but non-rotatably on the transverse axle and which may be manually slid into engagement with said offset locking member to lock the differential.

o In one form the transverse axle extends outwardly beyond the adjacent wheel hub and the locking means is in the form of a dog clutch having a plurality of said offset locking members mounted on the adjacent wheel hub and a complementary carrier mounted non-rotatably on and slidably along the extension of the axle beyond the adjacent wheel hub relative to the offset locking members for engagement with the offset locking members mounted on the free wheel hub.

This arrangement provides an axial locking movement between parts which rotate relative to one another during differential rotation whereby cyclic alignment for locking engagement will occur thereby facilitating ease of operation.

The differential assembly could be disposed substantially within the wheel supported by said one wheel hub. Suitably the differential is adapted to be so arranged that it is substantially concealed within the adjacent wheel and is exposed when the adjacent wheel is removed from the wheel hub for servicing or the like.

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which Illustrate a typical embodiment of the present invention and wherein:- FIG. 1 illustrates a mower assembly according to this invention; FIG. 2 is a pictorial view of a drive arrangement of the mower assembly illustrated in FIG. 1; FIG. 3 is a plan view of the drive assembly mounted in a

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o° i o ee o Such action pushes the push/pull link 66 causing translation of motion through the bell cranks 65 with resultant pushing of the actuating member 60 towards the forward drive pulley 33 and accompanying engagement of the clutch 36 therewith.

This arrangement is chosen such that the relatively long linkage assembly 68 which extends between the pivot link 67 and tne foot pedal 13 is maintained in tension when the drive mechanism is actuated in its forward direction. The linkage assembly 68 is of course placed in compression in reverse mode.

However in reverse mode, less drive torque is required to be transmitted from the drive assembly 25 and thus less force needs to be transmitted through the actuating member It will be seen from the above that the actuating linkage assembly 59 operates the actuating member 60 for reciprocal 15 axial motion along the driven shaft 31 and thus it provides an effective means of transferring movement of the foot pedal 13 to actuation of the drive assembly 25. Furthermore the drive assembly can be easily removed from the chassis 15 by releasing the quick connection pins 63 and the mounting bolts 73 which 20 secure the flangette bearings 35 to the chassis 15 and then by lifting the drive assembly 25 complete with the actuating member from the 'hassis.

For the purposes of replacing drive belts, sufficient clearance is left between the drive wheels 33 and 34 and the adjacent opening edge 78 such that a V belt may be inserted therebetween and placed into the grooves of the drive wheels 33 and 34. The belt may pass over the actuating member subsequent to the rear end of the latter being disconnected by the quick connect pin 63.

The actuating member 60 retains the bearing 47 between part circular portions 55 of identical overlapping arms 56 which are bolted together by through bolts as illustrated. The arms 56 are so formed that the shank portions are co-planar.

The bearing 47 is retained against axial movement relative to the arms 56 by forked retainer plates 57 fitted between the overlapped portions of the arms 56. Each plate 57 is forked at its inner end so as to neatly accommodate the periphery of the bearing 47 between the its fingers 58.

The linkage assembly 68 incorporates spring 72 disposed about the push/pull rod 73 an between an adjustable nut 76 on the rod 73 and an abutment collar 74 formed on an extension bar A further collar 77 is formed on the extension bar 75 to slidably locate the trailing end of the rod 73. Thus in use, the spring 72 limits the force applied to the actuating member for reverse operation with operation of the foot pedal 13.

The drive assembly 25 is suitably located within a square cutout 80 in a folded steel plate chassis 15. For this purpose the cutout is terminated by mounting flanges 81 folded from the opposed sides of the cutout 80. The flanges 81 are each provided with a doubler 82 which is suitably bolted thereto along the full length of the flange. Each doubler 82 is suitably in the form of a carrier plate which extends below 15 the chassis and provides mountings or a mounting for the rear axle assembly As shown in Figs. 4 and 5, the flanges 81 extend transverse to the shaft 31 from opposite sides of a relief cutout 83 formed in the sheet metal chassis adjacent the 20 opening 80 to enable the bearings 35 to extend dow-' beyond the upper face of the chassis. This arrangement permits the centreline of the drive shaft 31 to be disposed close to the chassis surface 84 such that axial loads applied through the drive shaft by the actuating mamber 60 do not reso in 25 significant flexing of the flanges 81. Thus oper-,ion of the drive assembly 25 by the actuating member 60 is enhanced.

Furthermore it will be seen that the sprocket 84 is located close to the forward drive pulley wheel 36.

Accordingly the:drive load path in the forward mode is minimised thus further minimising flexure within the shaft itself and assisting positive actuation of the drive. The above described arrangement also provides an advantage in that the sheet metal from which the chassis is formed may be minimised, maintaining a low chassis weight.

Belt tension is maintained in the secondary drive belt by adjustment means 100 which supports the idler pulley 20. The adjustment means 100 is illustrated in Fig. 8.

The adjustment means 100 is adapted for supporting the ii idler pulley 20 for movement al a slotted frame bracket 102.

The pulley 20 is mounted on a spindle assembly 103 rigidly attached to a slide bar 104 which is mounted within guide apertures 105 formed in end plates 106 and 107 of the frame bracket 102. The bar 104 is supported in use such that it extends parallel to the runs 108 of the drive belt 109 which passes about the pulley 20. The spindle 103 passes through a slide bearing 120 which engages about the edges of the slot 121 and stabilizes the pulley A spring pawl 122 attached at one end to the bracket 102 extends angularly to the bar 104 whereby its outer end 123 is biassed through is own resilience into engagement with the bar 104 and with a plurality of notches 124 formed along a portion of the bar 104. The pawl 122 permits the bar 104 to move 15 freely in the direction away from the belt runs 108, the ratchet direction, but prevents opposite movement towards the belt runs 108.

A tension spring 125 is attached at one end to the end plate 107 and extends alongside the bar 104 and its other end 20 connects to the bracket 126 fixed to the end 127 of the slide bar 104. The tension spring 125 forces the bar 104 in the ratchet direction. A spring release trigger 128 is fixed to the pawl 122 and extends away therefrom to protrude beyond the frame bracket 102 whereby the outer end 129 of the trigger 128 25 may be manipulated to deflect the pawl away from the slide bar 104. The deflected attitude of the spring pawl is illustrated in dotted outline at 130. The trigger is used when the spring 125 has been released from the bar 104 to enable the bar 104 to move freely in through the end plates 106 and 107 such as for moving the pulley to the rear 131 of the slot 121 to enable the belt 109 to be either removed or replaced, as shown in dotted outline at 132.

In use, as illustrated, a V-belt 19 which is to be tensioned is passed around the pulley 20. The tension spring 125 draws the slide bar 104 through the guide apertures 105 to tension the belt 19 while the outer end 123 of the spring pawl 122 rides up and over the notches 124 until the V-belt 19 has been drawn into a state of tension controlled by the force in the tension spring 125. The bar 104 is prevented from oscillating or reducing belt tension by engagement between the pawl end 123 and one of the notches 124. The spring 125 will automatically advance the bar 104 in the ratchet direction as the belt wears dr stretches and sufficient slack appears in the belt 109 such that the cumulative tension in the belt runs is less than the tension of the spring 125. The notches 124 are arranged close together such that such movement is accompanied by engagement of the pawl with the next notch.

When it is necessary to move the slide 102 back to a low belt-tension position, such as for changing the belt, the spring 125 is released and the trigger 128 is manipulated to release from the bar 104 allowing it to be slid through the guide apertures 105 and so position the pulley 20 that the belt 15 may be released therefrom.

Belt tension is maintained in the cutter drive belt 147 by adjustment means 135 which supports the idler pulley 28 at the front 136 of thd chassis about which the return run of the cutter belt 17 passes. The adjustment means 135 is illustrated 20 in Fig. 9.

The drive belt 17 passes forwardly from the engine mounted driving pulley 29 attached to a vertical-shaft motor 16 for return about idler pulleys 28 to the driven pulley 18. This arrangement provides a relatively long belt run to the driven pulley 18 which is advantageous for the purposes of raising and lowering the driven pulley 18 with the cutter housing.

The belt 17 passes from the smaller driving pulley 29 forwardly beneath the mower chassis 15, rotating a quarterturn to engage with the idler pulleys 28 before returning to the larger driven pulley 18. The idler pulleys 28 are supported for rotation on pulley carriers 147 and 148 which maintain the idler pulleys inclined at the correct angle to lead the lower runs of the belt 17 onto the larger diameter driven pulley 18.

The carriers 147 and 148 are substantially identical, however the carrier 147 carrying the idler pulley 28 engaged by the drive run of the belt 17 is bolted rigidly to the mower chassis 15 while the other carrier 148 is bolted to a U-shaped bracket 150 having apertured legs 151 supporting plastics bushes 152. The bushes 152 are slidable along a round shaft 154 secured at its ends by through bolting to a chassis front wall member 155 and rear wall member or bracket 156. The length of the shaft 154 is such as to permit substantial travel of the U-shaped bracket therealong without substantially changing the belt feed geometry. Accordingly the travel is able to accommodate a relatively large amount of stretch in the belt 17.

The carrier 148 is restrained from rotation about the shaft 154 by a stud 157 held captive in a mounting slot 160 in the chassis 140 and spaced from the shaft 154. The slot 160 is disposed parallel to the shaft 154. The stud 157 passes upwardly beyond :the slot 160 through a slotted pivot member 163 15 arranged above the chassis 15. The free end of this member 163 forms a pointer which indicates the limits of automatic adjustment of the moveable idler pulley 28.

Each carrier is provided with multiple pulley mounting apertures 165 to enable belt tension to be adjusted manually to 20 enable the automatic tensioner to maintain effective operation.

It will be seen that the shaft mounting of the carrier 148 provides a relatively large reciprocal movement of the carrier S whereby early stretching of the belt will not cause the carrier to travel its full extent and whereby early maintenance 25 associated with short travel adjusters is alleviated.

Furthermore the small mass of the reciprocating parts facilitates operation of the tensioner. If desired friction damping or other forms of damping may be utilised to damp the motion of the carrier 148.

The carrier 148 is controlled through a spring biassed push rod assembly 166 connected to one of the apertures 167 and an actuating lever 168 is used to provide the necessary control of the rod 166, including locking it in a retracted position to prevent drive being transferred through the drive belt 17. The push rod assembly 166 is shown disconnected in the drawings, however it will be apparent that the spring 170 urges the rod 171 substantially parallel to the shaft 154 so as to maintain appropriate tension in the belt 17. The bearing end 172 of the rod may be engaged in either aperture 167 to achieve the desired tension. Other forms of adjustment may also be provided as desired such as length adjustment of the rod 171.

As shown in Fig. 1 a grass catcher 30 may be fitted to the mower 10. Details of the grass catcher are illustrated in Figs. 11 and 12.

In Fig. 11, the dotted outline 180 represents the grass outlet of the cutter housing 14 and the dotted outline 181 represents the grass inlet of the catcher 30. The inlet 181 is maintained in alignment with the outlet 13 by engagement between an upstanding pin 182 fixed to the cutter housing and engaging through an aperture 184 of a flange 185 extending along the upper edge of the inlet 181. The flange 185 rests upon the cutter housing 14 to support the leading end of the 15 catcher 11 which is able to move up and down with height adjustment of the cutter housing 14. In this manner the leading end of the catcher 30 may be readily secured in position by lowering it to engage the aperture 184 about the pin 182.

20 The upper extremity of the grass inlet 181 of the grass catcher 30 is disposed below the top face 183 of the catcher housing 186 and the space between the top face 183 and the mounting flange 185 increases rearwardly from the leading edge of the grass outlet 180. This arrangement forms an air space 25 187 above the inlet 181 in which cut grass does not accumulate S" and which alleviates the build up of cut grass at the neck portion 190 of the grass catcher 10. Thus grass flows efficiently rearwardly from the grass catcher inlet 181 into the main body of the catcher 30. To facilitate grass flow, the rear side wall is formed of mesh as is the breathing panel 191 in the back wall/door 192.

The rear. of the catcher 30 is supported by a bar 193 extends transversely from the mower 10 which extends beneath the housing and is located in slotted brackets 194 fitted to the underside of the housing 186 whereby it may pivot about and slide along the bar 193. The rear closure door 192 is mounted along its inside edge on hinges 195 and a spring 196 selectively holds the door 192 in the closed or open position.

An upstanding strut 197 forms a door mounting for the spring and provides a handle which is accessible to the driver of the mower whereby the door 192 can be readily moved to the open position by a seated operator as illustrated in Fig. 12.

In use, the catcher 30 is fitted to a mower 30 by firstly connecting the cross bar 193 thereto to provide the rear pivotal support and subsequently supporting the front of the catcher 30 on the cutter housing 14 with pin 182 passing through the aperture 184. The catcher 30 may be manually moved in a longitudinal direction to permit operative alignment of the pin 182 with the aperture 184. After mowing, when the catcher is full, the user simply pivots the door 192 to its over-centre open position at which it is held by the spring 196, grasps the handle 198 and tilts the catcher 30 about the 15 bar 193 to tip the contents thereof through the open rear end 198.

As shown in FIG. 13 the axle assembly 210 includes a transverse axle 211 provided with keyed land portions 212 and S 213 at each end thereof. The axle 211 is also provided with a 20 fixed sun gear 214 adjacent keyed land portion 213. The sun gear has a collar 215 which is adapted to locate within the bushed hub 216 of a drive sprocket 217 provided with bolt apertures 218 through which bolts may pass to connect an open ended tubular housing 219 to an opposed end plate 220. A shim 25 221 is adapted to be inserted between the sprocket and the back face of the gear 214 so as to enable the mesh between the gear 214 and opposed planetary gears 222 supported in the housing 219 to be adjusted. The planetary gears 222 are mounted on respective stub axles 223 fixed to the housing 219.

The axle 211 is further provided with a bearing surface 225 on which a tubular stub axle 226 may rotate. The tubular stub axle 226 is formed integrally with a further sun gear 227 adapted to mesh with the planetary gears 222. A further shim 228 is provided for placement between the back face of the gear 227 and the end plate 220. The tubular stub axle 226 is also provided with an outer key 230 so that it may be locked to a wheel hub 231. The latter is provided with studs 229 which pass through the mounting apertures 232 in the wheel 233. At the other end of the axle 211 a further carrier 240 mounts on the keyed land portion 212 and connects to the wheel 241 through studs 242. The wheel 233 is adapted to be locked to the studs 229 through wheel nuts 245 which have extensions 246 formed thereon. The extensions 246 are adapted to engage within respective radial slots 247 in a locking plate 250 having a hub 251 which is keyed to the keyed land portion 213.

The arrangement is such that drive is transmitted to the housing 219 and~to either one or both of the sun gears 214 or 227 by the planetary gears 22. The latter assembly will provide a differential action between the wheels 233 and 241 in known manner. However if during use further drive is required in situations where one wheel may slip and cause drive to be lost, the differential assembly 300 may be locked by moving the 15 locking plate 250 along the keyed land portion 213 until the wheel stud extensions 246 engage within the slots 247. In this configuration neither wheel may spin independent of the other.

Both will be driven through the differential assembly 300 for simultaneous rotation.

20 From the above it will be seen that the differential can be formed inexpensively through using very simple components such as cropped tubing to form the housing and a simple dog S. clutch to provide the differential lock mechanism. Furthermore the differential may be associated directly with a sprocket or 25 the like with simple mountings as per conventional solid axle assemblies.

Figs. 14 anrid 15 illustrate sections of the differential assembly 300 in more detail. As illustrated, the differential housing 219 is machined from mild steel tubing and formed with opposing apertures 252 to accept the stepped threaded ends 253 of the pinion stub axles 254. The pinion stub axles 254 also pass through hardened and ground rectangular supporting blocks 255 which self align over the apertures and engage securely with the inner wall of the housing 219 when the securing nuts on the threaded ends 253 are tightened.

The corners of the hardened square blocks 255 bite into the relatively soft inner wall of the housing 219 and the square ends of the blocks 255 abut either end plate so that in use accurate location of the blocks and the planetary gears 222 supported thereby is provided. Furthermore, the through bolting apertures 218 are arranged at each side of the blocks 255 such that effective bolting together of the housing components may be achieved without distortion of the components.

The axle 211 is stepped at 256 to provide a locating shoulder for the side gear 214 which is secured thereto by a key 257. The keyed hub 251 of the locking mechanism is slidable along the end of the axle 211 and along the associated key 260 between disengaged and engaged positions, illustrated in full and dotted outlines respectively in Fig 14, and at which a sprung ball 261 engages with a respective one of the indents 262.

15 As shown in FIGS 16, 17 and 18 the differential assembly 265 includes a chain driven sprocket 266, an end plate 267 and a tubular housing 268 which enclose the remainder of the differential assembly. A first set of planetary gears 270 each having a spindle portion 271 is rotatably mounted on the 20 sprocket 266 and are adapted to mesh with a second set of planetary gears 272 each having a spindle portion 273 also rotatably mounted on the sprocket 266 whereby drive may be transferred by the enmeshed contra-rotating spur gears 270, 272 engaging with respective sun gears 280, 281. The first set of 25 planetary gears 270 has the spindle portions 271 distally disposed from the sprocket 266 whereas the second set of planetary gears 272 has the spindle portions proximally disposed to the sprocket 266.

The first set of planetary gears 270 mesh in orbiting relationship with a first sun gear 280 which is fixedly mounted on a main axle 282. In like manner, the second set of planetary gears 272 mesh in orbiting relationship with a second sun gear 281 which is fixedly mounted on a tubular stub axle 283. The main axle 282 passes through the tubular stub axle 283 and has a dog-clutch 284 mounted on a dog-clutch land 286 on the end of the axle 282 adjacent the differential side of the sprocket 266. The tubular stub axle 283 has a wheel mounting land 287 for mounting a wheel 288 thereon. The wheel includes a dog clutch engaging pin 289 for engaging the dog clutch 284. Another wheel (not shown) is mounted on the other end of the main axle 282.

The differential housing is sealed by oil seals 290, one of which seals the housing adjacent where the main axle 282 passes through the sprocket 266 and another which seals the housing adjacent where the stub axle 283 passes through the end plate 267.

If during use, drive is required in situations where one wheel may slip and cause drive to be lost, the differential assembly 265 may be locked by moving the dog clutch 284 axially along the land portion 286 until the dog clutch 284 engages with the engaging pin 291 on the wheel 288. In this configuration neither wheel may spin independently. Both will 15 be driven through the differential assembly 265 for simultaneous rotation.

As shown in FIG. 19 the differential lockout mechanism may be substituted by a clutch assembly 300 whereby the degree of relative rotation between the inner axle 301 and the outer 20 tubular axle 302 through the differential 303 is selectively variable. In this embodiment the differential lockout mechanism 300 is in the form of a clutch assembly 304 having a first clutch plate 305 secured to the wheel 306 by the wheel studs 307 and a second clutch plate 308 keyed to the shaft 301 25 by key 309 for free sliding movement therealong. Friction facings 310 are provided as illustrated. The end of the shaft 301 is couterbored and threaded at 311 to receive a finger operable adjusting nut 312 through which axial pressure may be applied through the collar 313 to the clutch plate 308 so as to force the clutch plate 308 into engagement with the clutch plate 305. A spring 314 is interposed between the hub 315 of the clutch plate 308 and the collar 313. The finger nut 312 may be tightened to effectively lock the shaft 301 to the shaft 302 or loosened to provide full differential action. Of course the finger nut may be adjusted intermediately above positions to provide a limited slip facility with selected slip being available.to the user.

Claims (10)

1. 2. A ride-on mower as claimed in claim 1, wherein said gear case is formed of components which bolt together and which are bolted together by bolts which bolt the sprocket to the gear case.
2. 3. A ride-on mower as claimed in claim 1 or claim 2, wherein said transverse axle provides a locating 'aoulder facing said one wheel hub for operatively locating said other sun gear.
3. 4. A ride-on mower as claimed in claim 3 and including drive means for drivingly connecting said other sun gear to said transverse axle when located against said shoulder. A ride-on mower as claimed in claim 4, wherein said drive means comprises a key located in a recess in said transverse axle and engageable with a keyway formed in said other sun gear.
4. 6. A ride-on mower including a chain driven reversible rear drive axle assembly of the type wherein: a differential gear 21 case is mounted rotatably on and supported by a transverse axle which supports respective wheel hubs at opposite ends thereof and which is supported for rotation by spaced chassis mountings intermediate said wheel hubs and through which spaced chassis mountings the transverse axle is attached to the mower's chassis; the gear case is mounted on the transverse axle and one wheel hub is rotatable about the transverse axle; a driven sprocket for the chain drive is attached to the gear case for driving the reversible rear drive axle assembly; the gear case includes a housing which extends co-axially of the transverse axle and which housing carries a differential gear set having opposed differentially driven sun gears supported in axially *spaced relationship on the transverse axle; the sun gear nearest said one wheel hub is rotatable about the transverse axle and is drivingly connected to said one wheel hub, and the other sun gear and the other wheel hub are locked for rotation with the transverse axle, and characterised in that:- the gear case includes fixed end walls at the opposite ends 0* C thereof which enclose the sun gears and planetary gears within the housing; the sun gear nearest said one wheel hub is drivingly connected to said one wheel hub by a tubular portion which passes rotatably through the fixed end wall interposed between said one wheel hub and the sun gear nearest said one wheel hub, and the transverse axle passes rotatably through the other end wall and said tubular portion. 22
5. 7. A ride-on mower including a chain driven reversible rear drive axle assembly as claimed in any one of claims 1 to 6 and further characterised in that there is provided selectively engageable differential locking means operable and disposed externally of the gear case and at the side of said one wheel hub which is remote from the gear case for effecting locking of the gear case assembly for rotation with said transverse axle and with said one wheel hub, whereby the respective wheel hubs are locked for rotation in unison with both said transverse axle and said gear case.
6. 8. A ride-on mower as claimed in claim 7, wherein the differential locking means locks together any of the differential components which can otherwise rotate differentially. 15 9. A ride-on mower as claimed in claim 7 or claim 8, wherein the differential locking means includes an offset locking S.member which is supported by and extends from said one wheel hub offset from said transverse axle. A ride-on mower as claimed in claim 9, wherein said offset locking member is fixed to said one wheel hub and is engaged by a locking plate supported slidably but non-rotatably on the transverse axle and which may be manually slid into engagement with said offset member to lock the differential. 1. A ride-on mower as claimed in claim 10, wherein said offset locking member is constituted by an extension of a wheel stud on said one wheel hub.
7. 12. A ride-on mower as claimed in claim 9 to 11, wherein said offset locking member constitutes one of a plurality of said offset locking members mounted on said one wheel hub and said locking plate engages all said locking members. 10 oo, S ooo •e 15 eeo
8. 13. A ride-on mower as claimed in any one of the preceding claims, wherein said gear case is disposed substantially within the wheel supported by said one wheel hub.
9. 14. A ride-on mower as claimed in claim 8, wherein said selectively engageable differential locking means is a finger adjustable clutch assembly which may be tightened to effect locking of the gear case assembly for rotation with said transverse axle and with said one wheel hub, or loosened to provide full differential action or adjusted to provide a limited slip facility between the gear case assembly, said transverse axle and said one wheel hub. A ride-on mower as claimed in any one of claims 6 to 14, wherein said sun gears are spur gears and said differential gear set includes a first pair of planetary spur gears meshed with one said sun gear and with respective ones of a second set of planetary spur gears meshed with the other sun gear.
10. 16. A differential drive axle assembly substantiafly as hereinbefore described with reference respective ones of the accompanying drawings. DATED THIS Third BARTLEM PTY LTD BY DAY OF December 1997 PIZZEYS PATENT TRADE MARK ATTORNEYS o o c D o 23 ABSTRACT An axle assembly [210] is provided which is suitable for driving chain driven vehicles. The axle assembly [210] includes an inner axle [211] which extends between spaced wheels [233/241] and through the differential drive [300] intermediate the wheels and which provides a differential drive between the inner axle [211] and the differential drive housing [219]. A tubular axle [226] extends from one side of the differential housing [219] and concentric with the inner axle [211]. The tubular axle [226] supports one wheel and the inner axle supports the other wheel and engaging means such as the locking plate [250] or a clutch are provided at a common end of the inner and tubular axles to lock one axle to the other or permit a selected amount of slip between the axles. 44 *o* o*o *f o