AU698806B2 - Improvements to power driven mowers - Google Patents

Description

IIIICI L- I- 1 "IMPROVEMENTS TO POWER DRIVEN MOWERS" This invention relates to differential locking of chain driven reversible rear drive axle assemblies. This application is associated with my earlier provisional patent application PK6740.

This invention has particular reference to chain driven reversible rear drive axle assemblies for power driven rideon mowers as described in my co-pending international patent application No. PCT/AU91/00176 and for illustrative purposes this invention will be described in relation the ride-on mowers.

r, Many domestic and ride-on mowers have driven rear wheels utilising a simple drive train to transmit power from the motor to the rear wheels. Typically the drive is transmitted by belts or chains to a transverse rear axle which supports the rear wheels. This system is generally satisfactory.

~However as the width of mowers increase tho disadvantages Cinherent in such drive systems becomes more noticeable. Such disadvantages can be overcome to a large extent by the Ot 20 provision of a differential in the drive train zo the rear wheels. The differentials available to date have not suited the simple drive trains which are utilised in most mowers and additionally such differentials have not had the ability to be selectively utilised or locked. Furthermore, the locking mechanisms for such differentials have been difficult and inefficient in use and/or increased the risk of damaging the iii 313 U-U i n drive mechanism and/or wheel mountings.

This invention aims to alleviate the abovementioned disadvantages and to provide a chain driven reversible rear drive axle assembly for a ride-on mower which will be reliable and efficient in use.

With the foregoing and other objects in view, this invention in one aspect resides broadly in a chain driven reversible rear drive axle assembly for a ride-on mower, including:a transverse axle supporting respective wheel hubs at i opposite ends thereof one hub being freely rotatable about 'said transverse axle and the other hub being fixed to said *transverse axle; a differential gear case mounted rotatably on and supported by said transverse axle and forming a housing extending along the transverse axle; a driven sprocket for the chain drive attached to the gear case; a pair of opposed planetary gears supported by said 20 housing for orbital motion about the transverse axle; opposed sun gears supported in axially spaced relationship along and co-axially about the transverse axle and within said housing and meshed with said opposed planetary gears for differential rotation thereby; a tubular stub axle rotatable about said transverse axle and drivingly connected to said one hub and the sun gear

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k n- C:- -TJF7~-- i 3 which is nearest said one hub, the other sun gear being locked for rotation with said transverse axle, and an externally accessible locking member associated with said one hub and manually moveable to a locking position at which it locks said one hub for rotation with said gear case and said transverse axle.

Preferably the outer stub-axle includes a non-circular locking socket facing said locking member mounted on the transverse axle and said locking member includes a correspondingly shaped spigot which may be selectively I engaged in said socket, said spigot and said socket. It is t t also preferred that said spigot and said socket are of .rectangular section and that the positioning means includes biassing means biassing said spigot into engagement with said socket and latching means is provided for maintaining said B t spigot disengaged from said socket against said biassing us, t tmeans.

i U U *1tt Suitably the transverse axle extends outwardly beyond the hub which is freely rotatable about said transverse axle and the locking member is in the form of a dog clutch engageable with the freely rotatable hub. Suitably the dog clutch is in the form of a carrier mounted non-rotatably on and moveable along the transverse axle for engagement with the corresponding clutch member on the freely rotatable hub.

In order that this invention may be more readily understood and put into practical effect rrference will now 13 tT:

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I be made to the accompanying drawings and wherein FIG. 1 is a cross-sectional view illustrating the operative ar-cangement of a preferred embodiment the differential, axle housing and locking means; FIG. 2 is a partly cut away exploded view of a differential locking means according to the embodiment shown in FIG. 1; FIG. 3 is a cross-section of the differential locking means according to the embodiment shown in FIGS. 1 and 2 in the disengaged position, and FIG. 4 is a cross-section of the differential locking means according shown in FIG. 3 in the engaged position.

r Referring to FIGS. 1 to 4, the axle assembly 10 includes a transverse axle 11 provided with keyed land portions 12 and 13 at each end thereof. The axle is also provided with a cc c L fixed sun gear 14 adjacent the end 13. The sun gear has a C C C C collar 15 which is adapted to locate within the bushed hub 16 Ct It of a drive sprocket 17 provided with bolt apertures 18 through which bolts may pass to connect an open ended square 20 housing 19 to an opposed end plate 20. A shim 21 is adapted to be inserted between the sprocket and the back face of the gear 14 so as to enable the mesh between the gear 14 and opposed planetary gears 22 supported in the housing 19 to be adjusted. The planetary gears 22 are mounted on respective stub axles 23 welded to the housing 19.

The axle 11 is further provided with a bearing surface i i ii i ;i i: i

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I I Ic It c 4S* on which a tubular stub axle 26 may rotate. The tubular stub axle 26 is formed integrally with a further sun gear 27 adapted to mesh with the planetary gears 22. A further shim 28 is provided for placement between the back face of the gear 27 and the end plate 20. The tubular stub axle 26 is also provided with an outer key so that it may be locked to a wheel carrier 31, and secured in place thereon with a clamp screw 35 and clamp nut 36. The latter is provided with studs 34 which pass through the mounting apertures 32 in the wheel 33. At the other end of the axle 12 a further carrier mounts on the land 12 and connects to the wheel 41 through studs 42. The wheel 33 is adapted to be locked to the studs 34 through wheel nuts, one of which is shown at An engagement plate 50 having apertures 51 is mounted on 15 the studs 34 on the wheel carrier 31. The engagement plate has a shaped aperture 53 of complementary shape to an engagement block 44 which is rotatably fixed on the keyed land portion 13 of the main axle 11.

The axle assembly 10 will provide a differential action between the wheels 33 and 41 in known manner until and/or until the engagement block 44 is moved axially to engage the shaped aperture 53 in the engagement plate 50. If during use drive is required in situations where one wheel may slip and cause drive to be lost, the differential assembly 10 may be locked by moving the engagement block 50 axially along the extension portion 13 until the engagement block 44 engages i:: i iii ii e 1 )i tvtt IL I t t t I /I I

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ritz cI IC I IL I I Ir I I (II within the shaped aperture 53 in the engagement plate 50 as shown in FIG. 4. In this configuration neither wheel may spin independently and both will be driven through the differential assembly 10 for simultaneous rotation.

If, on the other hand, differential drive is required for cornering and such like, the engagement block 44 is moved axially to disengage the engagement plate 50 as shown in FIG.

3 so that the wheels 33 and 41 are driven differentially.

The engagement block 44 is provided with a pivotable handle 46 and may be pivoted from an engaged position as shown in FIG. 4 to a disengaged position as shown in FIG. 3.

A retaining washer 43 retains an engagement spring 47, the retaining washer 43 being secured to the end of the shaft 11 by a retaining screw 48. The engagement block 44 is biassed towards the engagement plate 50 by a locking spring 47 which is compressed between an end face of the engagement block and the retaining washer 43. The pivotable handle 46 may be used to pull the engagement block out of the shaped aperture 53 in the engagement plate 50 and pivoted over the distal end portion of the retaining washer 43 to hold the engagement block 44 in the disengaged position.

From the above it will be seen that the differential can be formed inexpensively through using very simple components such as cropped square tubing to form the housing and a simple dog clutch to provide the lock mechanism. Furthermore the support of the differential in the wheel cavity enables yTi, jii r an exposed drive shaft to extend across the macl'ine from the drive sprocket to the opposite wheel thereby giving maximum ground clearance between the wheels. Such arrangements enable existing chassis mounting and drive arrangements in ride on mowers and the like to be utilised without major modifications.

In a typical installation the rear axle assembly illustrated herein may be driven through a reversible endless belt drive assembly of the type having opposed clutch plates of a clutch assembly adapted for reciprocation along an i t4 output shaft by a clutch actuating mechanism for engagement ,01. with either one of a pair of belt driven contra-rotatable too* pulley wheels. The latter are supported for free rotation on Si the output shaft and are coupled thereto through the clutch assembly for driving engagement in forward or reverse t rotation, the sprocket 17 being chain driven or belt driven if desired from the output shaft.

The differential assembly illustrated in Figs. 1 to 4 may be any form of differential wherein a main axle 20 supporting one wheel is provided with a free wheeling stub axle for the other wheel, including the type of differential disclosed in our copending patent application No. PK 2972 wherein the planetary gears 22 are replaced with sets of coaxial planetary gears. In such an arrangement, each sun gear 14 and 27 is a spur gear and each sun gear 14 and 27 is provided with one or a plurality of planetary spur gears, the \\7i i i I 8 respective planetary gears or sets thereof meshing with each other to provide the differential drive. In such an arrangement, the planetary gears are supported on full axles rather than stub axles, and the differential housing may be made smaller in volume due to there being no pitch cone apex which bevelled gears would be required to surround.

It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to crrrc r c fall within the broad scope and ambit of the invention as claimed in the following claims.

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Claims (9)

1. A chain driven reversible rear drive axle assembly for a ride-on mower, including:- a transverse axle supporting respective wheel hubs at opposite ends thereof one hub being freely rotatable about said transverse axle and the other hub being fixed to said transverse axle; a differential gear case mounted rotatably on and supported by said transverse axle and forming a housing extending along the transverse axle; *tit a driven sprocket for the chain drive attached to the C 4 gear case; Vt it a pair of opposed planetary gears supported by said housing for orbital motion about the transverse axle; opposed sun gears supported in axially spaced "tit, relationship along and co-axially about the transverse axle and within said housing and meshed with said opposed planetary gears for differential rotation thereby; a tubular stub axle rotatable about said transverse axle and drivingly connected to said one hub and the sun gear which is nearest said one hub, the other sun gear being locked for rotation with said transverse axle, and an externally accessible locking member associated with *said one hub and manually moveable to a locking position at which it locks said one hub for rotation with said gear case -4A ML namm" 'A and said transverse axle.

2. A chain driven reversible rear drive axle assembly as claimed in claim 1, wherein said externally accessible locking member is slidable non-rotatably along said transverse axle for locking engagement with said one hub.

3. A chain driven reversible rear drive axle assembly as claimed in claim 2, wherein said one hub includes a non- circular locking socket disposed co-axially of said transverse axle and facing a correspondingly shaped spigot 10 portion of said locking member.

4. A chain driven reversible rear drive axle assembly as claimed in claim 3, wherein said spigot portion and said 4 4 locking socket are of rectangular section. S '1

5. A chain driven reversible rear drive axle assembly as claimed in any one of the preceding claims, and including r biassing means biassing said locking member into its locking position and latching means for maintaining said locking member disengaged against said biassing means.

6 A chain driven reversible rear drive axle assembly as claimed in any one of the preceding claims, wherein said 2 housing encloses said sun gears and planetary gears and said 4LU Y' -i Fi m *I I I C is.. *r I I 11 tubular stub axle and said transverse axle pass sealably through opposed end walls of said housing.

7. A chain driven reversible rear drive axle assembly as claimed in any one of the preceding claims, wherein said gear case is mounted on the transverse axle closely adjacent said one wheel hub.

8. A chain driven reversible rear drive axle assembly as claimed in any one of the preceding claims, wherein said locking member is disposed at the side of said one wheel hub which is remote from the gear case.

9. A drive axle assembly substantially as hereinbefore described with reference to the accompanying drawings. C. SIC II~ I~ C I ct*r -i 1; rv i DATED THIS Sixth DAY OF October BARTLEM PTY LTD BY PIZZEYS PATENT AND TRADE MARK ATTORNEYS

1998. i i i I; ;c~-CI i-IC: i-i i i i i I 12 ABSTRACT A locking assembly is provided for selectively locking independently rotatable concentrically disposed shafts such as the shafts [11, 26] of a axle assembly The locking assembly has a mounting plate [50] on the outer shaft [26] and a selectively operable locking block [44] slidable non- rotatably along the inner shaft The plate [50] has a square socket [53] formed therein and into which the square end of the locking block [44] may engage to lock the inner and outer shafts [11, 26] together for corresponding rotation. A spring [47] biases the locking block [44] into engagement with the mounting plate [50] and a latch [46] pivotally connected to the block [44] latches over the end of the inner shaft [11] to maintain the locking block [44] spaced from the mounting plate I! 1 9