Background to the Invention.

A typical application for couplings of the above-described type is the direct drive between the crankshaft of a small industrial petrol engine and an article to be driven. For example the article to be driven may be a rotary chipper blade utilised for chipping green garden waste, twigs and small branches and the like in a garden mulcher. For illustrative purposes only, reference will be made hereinafter to this application.

Typically the output shaft of a power module such as a small petrol engine incorporates a suitable locking feature such as a keyway or thread for effecting a non-slip driving connection with the driven member connected thereto. Unfortunately in many production installations there is slight play between the key and the keyways in the output shaft and the drive coupling with the result that in the above types of applications the key is often hammered and wears at an unduly fast rate.

Our earlier filed International Application PCT/AU99/727 with publication No.

W00013797 describes various forms of garden refuse shredding apparatus suitable for shredding leaves, twigs, palm fronds and small branches. The present invention has application in such arrangements and also to provide improvements to the drive shaft mountings in such shredding apparatus.

It is an object of the present invention to provide a direct drive coupling which is an improvement over those known in the prior art.

Summary of the Invention With the foregoing in view, this invention in one aspect resides broadly in an apparatus including: an output shaft formed with a keyway; a coupling part formed with a coupling socket to receive the output shaft; a slot in the socket for closely accommodating a key supported in the keyway, a collar which extends about the slotted portion of the coupling part; and clamping means engageable with the outer face of a key in the keyway to urge the key into tight engagement with the keyway.

The apparatus may be configured for shredding garden refuse.

In another aspect this invention resides broadly in a coupling for coupling an article to be driven to an output shaft of a power module, said shaft having a keyway formed therein, the coupling including :- a coupling part formed with a coupling socket to receive the output shaft; a slot in the socket for closely accommodating a key supported in the keyway, and a collar which extends about the slotted portion of the coupling part and provided with clamping means engageable with the outer face of a key in the keyway to urge the key into tight engagement with the keyway.

The coupling part may include an elongated drive shaft having a coupling socket formed at one end and a further coupling formation at the other end. The coupling part may be the hub of a rotary member, such as a gear or crank shaft. The

coupling part may provide a bearing land adjacent the end of the output shaft and, if desired, such as for supporting a rotary chipper member, a mounting for the rotary chipper member adjacent the bearing land.

The slot in the socket may extend in from the open end of the socket or it may be a bounded slot located in spaced relationship with the open end of the socket. In the latter case the length of the slot is such as to enable the key to be engaged with and released from the keyway through the slot.

The coupling part may be formed so that the key accommodated therein is either flush with or disposed beneath the surrounding portion of the coupling part.

The inside face of the collar may contact the key supported in the slot or it may be spaced from the key. If desired the collar may be slotted to accommodate a key which protrudes from the coupling part.

The clamping means may be integral with or separate from the collar. For example the clamping means may be a wedge to be driven between the collar and the key or it may be a cam lock arrangement supported by the collar or cam threaded together and locked. In one suitable form the clamping means includes one or more grub screws supported in the collar and rotatable into engagement with the outer face of the key.

According to a further aspect of the present invention there is provided a method of coupling an article to be driven to an output shaft of a power module such as an electric motor, the shaft having a keyway formed therein, the method including :- providing a coupling part formed with a socket to receive the output shaft; providing a slot in the socket for closely accommodating a key supported in the keyway;

providing a collar to extend about the slotted portion of the coupling part; providing the collar with clamping means engageable with the outer face of the key, and assembling the coupling part to the output shaft by: aligning the slot with the keyway; accommodating the key in the keyway and slot ; placing the collar about the slotted portion of the coupling part and operating the clamping means to urge the key into tight engagement with the keyway.

Brief Description of the Figures 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 application utilising the present invention and wherein:- FIG. 1 is a sectional view through the coupling between a shredder disc and the output shaft of a small industrial petrol engine, and FIG. 2 is a side view in the direction A of Fig. 1.

Detailed Description of Preferred Embodiment In a typical garden shredder an engine mounting upstand 10 is supported on the housing 11 surrounding the chipper disc part of which is shown at 12. Disc 12 is coupled to and driven by the output shaft 13 of a lightweight petrol internal combustion engine by a directed drive coupling 14, as illustrated, which is supported by a self aligning bearing15 mounted on the housing 11. A suitably aligned ball, roller or plain bearing might also be used in place of self-aligning bearing 15.

In the embodiment depicted, the coupling 14 includes a stub-shaft 16 provided with a socket 17 in its upper end for receiving the reduced portion 19 of the output shaft 13. Reduced portion 19 is formed with a keyway 20 for driving

engagement with the coupling 14. The stub shaft 16 is terminated by a base flange 23 to which the chipper disc 12 is bolted by bolts 22. A further long bolt 18 locates and secures the coupling 14 directly to the output shaft 13. Self-aligning bearing 15 incorporates a cast metal support housing 24 bolted to the upper wall of housing 11.

A key 30 is supported in the keyway 20 and protrudes beyond the output shaft portion 19 to engage closely within a slotted aperture 31 formed in the upper portion of the coupling stub-shaft 16. A square or half-moon key of the"Woodruff' type might be used in place of the key 30. The radius dimension to the outside face of the stub-shaft 16 from the drive axis 25 is the same as the radius from the drive axis 25 to the outer face of the key 30 and the length of the slot 31 through the upper portion of the stub shaft 16 is slightly greater than the length of the key 30.

Furthermore, the length of the slot 31 is also slightly greater than the length of a close fitting collar 32 which slides over the outer face of the stub-shaft 16 to be positioned in axial alignment with the slot 31. Alignment can be readily achieved by sighting the end portions of the slot 31 at either end of the collar 32. Visibility of the slot 31 also assists in ready alignment of grub screws 33 threadedly supported in the collar 32 with the key 30, again by aligning the grub screws with the visible portions of the slot 31 at the opposite ends of the collar 32. The grub screws 33 are maintained tight so as to push the key 30 into tight engagement with the base of the keyway 20.

In use, the coupling 14 is connected to the shaft 13 by feeding the end 19 of the shaft 13 into the socket 17 and then rotating the coupling 16 until the slot 31 overlies the keyway 20. In that position, the key 30 may be introduced through the slot 31 into the keyway 20 so that one full side face of the key 30 is in driving engagement with corresponding sides of the keyway 20 and slot 31 respectively.

Subsequently the collar 32 is slid from a position above the coupling 14 onto the coupling 14 and aligned so that it is centred over the slot 31 with the grub screws 33 in line with the key 30. The grub screws 33 are then fully tightened to force the grub screw into tight engagement with the key 30. (Alternatively the coupling could also be arranged so that the grub screws lock on socket 17.) Tightening of the grub screws clamps the assembly together and assists in preventing any relative movement between the key 30 and the drive shaft 13 and coupling 14. This alignment is more clearly illustrated in Fig. 2.

The above-described arrangement maintains the outside of the stub shaft 16 at a minimum radius as indicated above. Consequently the self-aligning bearing 15, that supports the lower end of the stub-shaft 16, has an internal diameter which is not much greater than the external diameter of the drive coupling 14. This size is more than adequate for the expected loads from a given shaft diameter and provides an economical solution to maintaining support close to the rotary chipper disc 12. By maintaining support close to chipper disc 12 bending loads, which may be induced in the stub-shaft 16 and engine drive shaft 13 are minimised. Such bending loads are undesirable as they may have an adverse effect on the engine's crankshaft or the bearings therefore.

It will be seen that the heads 35 of the Allen head bolts which secure the bearing support housing 24 to the upper wall 11 are utilised as anvils across which profiled blades 36 pass closely during their rotation with the disc 12 for chopping up fibrous material which may move towards the stub-shaft 16. It will be realised by those skilled in the art that any suitable bolt or pin might be used in place of the Allen bolts. Down facing or up-facing suitably placed pins bolted or welded to chipper disc 12 or upper wall 11 could also be used to achieve the chopping action provided that

they are arranged to pass very close to profiled blades 36 on all sides. It will be noted that a dependent annular flange 37 surrounds the mounting flange 23 supported at the lower end of the stub shaft 16.

It will of course be realised that the above described embodiment has been given only by way of illustrative example of the present invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth in the following claims.