Field of the Invention The present invention relates to portable hand held appliances of the type generally used in lawn and garden applications, (but is not limited thereto) and which are powered by a single cylinder internal combustion engine.

Background Art Such appliances include (but are not limited to) lawn edgers, line trimmers, cultivators and blowers. Typically the single cylinder internal combustion engine has been a two stroke engine. However, in recent times small four stroke engines have been utilised in such appliances.

Such appliances can be categorized into three groups defined by the position of the operator in use, relative to the engine's output shaft. For example, in a lawn edger and in cultivators, the operator stands immediately behind the engine but in line with the output shaft which extends forwardly relative to the operator. As a consequence, for both a cultivator and a lawn edger, if the operator is facing north, then the output shaft points north and the exhaust outlet is directed towards the east. Such compass references will be used hereafter to signify relative orientations.

For a motorised hand held blower, an air impeller is driven by the engine and blows high velocity air in front of the operator. For such a blower, if the operator is facing north, then the exhaust outlet is directed towards the north.

However, for a line trimmer, and for a brush cutter, the operator stands alongside the engine. Thus if an operator of a line trimmer or brush cutter is facing north, the output shaft points north and the exhaust outlet is directed to the south.

Also the air flow used for cooling the engine, which is heated to a significant extent as it passes over the engine's cylinder, is expelled away from the engine. This expulsion is usually in a rearward direction which is in line with the crankshaft and extends longitudinally from the engine.

However, in the case of the abovementioned lawn edger and cultivator appliances this hot air has to be diverted from its usual south direction and away from the operator who stands to the south of the engine (and facing north). Ideally this hot air should be deflected by an angle of from 45° to 90°. That is, the heated air is expelled in a south easterly to easterly direction from the engine of a lawn edger or cultivator.

The hand blower is intended to be used with either hand, ie a north facing operator can hold the blower in his left hand and stand to the east of the blower, or alternatively hold the blower in his right hand and stand to the west of the blower. In both instances the appliance is blowing high velocity air (to transport leaves etc) to the north (with the exhaust nozzle also directed north). The engine shaft in these circumstances is directed towards the west. However, as the operator can stand in the alternative eastern side position of the engine, the blower has its engine cooling air, directed away from the operator at an angle of from 45° to 90° from the longitudinal axis of its crankshaft. That is, the heated air should be expelled in a north east to north direction when the operator is facing north and the blower is blowing north.

As a consequence of these different categories and requirements, it has been hitherto necessary to have three models of engine for such appliances. The engines are provided with different mufflers, and different cowlings, so that the manufacturers of all three categories of such appliances need to produce and/or keep in stock three different types of engine, even though these three types could be different versions of the same basic engine. As a result of this requirement to produce and/or stock three engine types, economies of scale are not always able to be achieved.

The genesis of the present invention is a desire to provide a multi-purpose internal combustion engine platform, and parts and accessories therefor, such that the one engine platform can be used for the different groups of appliances. Summary of the Invention In accordance with a first aspect of the present invention there is disclosed an exhaust muffler for a portable single cylinder internal combustion engine, said muffler having a muffler body, and a gas inlet leading into said body and dimensioned to be connected to said cylinder, wherein said muffler has two exhaust nozzle mounts each oriented in a different direction and each comprising an exhaust opening in said muffler body and at least one releasable engagement means adjacent said exhaust opening and wherein one of said exhaust nozzle mounts has an exhaust nozzle outlet releasably mounted over its said opening and the other of said exhaust nozzle mounts has a cover releasably mounted over its said opening, said exhaust nozzle outlet and said cover being interchangeable.

In accordance with a second aspect of the present invention there is disclosed an engine cowling for a portable single cylinder internal combustion engine having a crankshaft axis and having an exhaust muffler, said cowling being adapted to overlie said muffler, having two exhaust nozzle apertures each oriented in a different direction, a plurality of air exit slots located and an air deflector means to deflect air passing over said cylinder to cool same out of said air exit slots and at an angle of approximately 45°-90° to said crankshaft axis.

In accordance with a third aspect of the present invention there is disclosed a multi-purpose internal combustion engine platform having the abovementioned muffler and/or the abovementioned cowling.

In accordance with a fourth aspect of the present invention there is disclosed a set of portable hand held appliances each powered by a single cylinder internal combustion engine, said set comprising appliances categorized into two groups defined by the position of the exhaust outlet, said set further comprising the same or substantially the same engine platform mounted on each said appliance, save that the exhaust outlet of the mufflers on the engines of said first group of appliances are oriented in a first direction, and the exhaust outlet of the mufflers on the engines of said second group of appliances are orientated in a second direction. In accordance with a fifth aspect of the present invention there is disclosed a portable single cylinder air cooled engine having an exhaust muffler with a muffler body, a gas inlet leading into said body from said cylinder, and two exhaust nozzle mounts each orientated in a different direction; said engine further having an engine cowling means to deflect air flowing past said cylinder to cool same, said cowling means including two exhaust nozzle apertures corresponding to said exhaust nozzle mounts and a plurality of air exit slots positioned intermediate said exhaust nozzle apertures.

In accordance with a sixth aspect of the present invention there is disclosed a method of operating an air cooled single cylinder internal combustion engine having a muffler with an exhaust nozzle, an apertured engine cowling and a crankshaft having an axis, said method comprising the step of deflecting air over said cylinder to cool same whereby the air heated by said cylinder exits via said cowling in a direction which is inclined to said crankshaft axis and is inclined to each of two said exhaust nozzle apertures in said cowling.

In accordance with a seventh aspect of the present invention there is disclosed a set of portable single cylinder air cooled engines each having an engine cowling including two exhaust nozzle apertures, wherein said set of engines is formed from a first plurality of engines and a second plurality of engines and a first plurality of mufflers and a second plurality of mufflers, the mufflers of said first plurality having an exhaust nozzle mounted in a first direction aligned with one of said exhaust nozzle apertures and the mufflers of said second plurality having an exhaust nozzle mounted in a second direction aligned with the other of said exhaust nozzle apertures.

Brief Description of the Drawings A preferred embodiment of the present invention will now be described with reference to the drawings in which: Fig. 1 is a perspective view from above and to the side of a lawn edger in accordance with the preferred embodiment of the present invention, Fig. 2 is an enlarged view of the engine of the lawn edger of Fig. 1, Fig. 3 is a similar view of the engine of Figs. 1 and 2 but with the cowling covering the exhaust muffler removed, Fig. 4 is a perspective view of a line trimmer in accordance with the preferred embodiment of the present invention, Fig. 5 is an enlarged perspective view of the engine of the line trimmer of Fig. 4, Fig. 6 is a perspective view similar to Fig. 5 but with the engine of Figs. 4 and 5 having the cowling covering the exhaust muffler removed, Fig. 7 is a perspective view of a blower including the high velocity air outlet tube, Fig. 8 is a view similar to Fig. 7 but at an enlarged scale and with the high velocity air outlet tube of Fig. 7 and the engine cowling removed, Fig. 9 is a plan view of the edge trimmer of Fig. 1 showing the operator's position in use, Fig. 10 is a plan view of the blower of Fig. 7 showing the two possible positions of the operator in use, Fig. 11 is a perspective view of the exhaust muffler used in the appliance of Figs. 1-3, and Figs. 7 and 8, Fig. 12 is an exploded perspective view of the exhaust muffler of Fig. 11, Fig. 13 is a perspective view of the exhaust muffler used in the appliance of Figs. 4-6, Fig. 14 is an exploded perspective view of the exhaust muffler of Fig. 13, Figs. 15-18 correspond to Figs. 11-14 but illustrate a muffler of a second embodiment, and Fig. 19 is an exploded perspective view of the engine cowling showing details of an assembly aid.

As seen in Figs. 1-3, a first portable appliance powered by a single cylinder internal combustion engine is a lawn edger 1 of the general type described in the present applicants' US Patent No. 5,826,667. Similar appliances include cultivators such as disclosed in the present applicants' Australian Patent Application No. 2004 902 874 and golf bunker trimmers such as those disclosed in the present applicants' Australian Patent Application Nos. 2004 201 836 and 2004 201 840. The lawn edge trimmer 1 has an engine 2, a pair of handles 3 and a ground engaging wheel 4. The appliance 1 has a shaft 6 (not illustrated but within the casing) which is driven by the engine 2. In operation as best seen in Fig. 9 the operator 100 stands between the handles 3. Thus if the operator is regarded as facing north, the shaft 6 extends forwardly of the operator in use, or to the north.

As seen in Fig. 2, the engine 2 has a cowling 8 with two exhaust nozzle apertures 9, 10 which are oriented in two directions (south and east respectively) which are substantially perpendicular to each other. The cowling 8 also has a multiplicity of substantially parallel arranged air exit slots 11. As best seen in Fig. 3, where the cowling 8 is removed, the engine 2 has an exhaust muffler 12 with an exhaust nozzle outlet 13 which is arranged to direct exhaust gases through the exhaust nozzle aperture 10 of Fig. 2 and thus away to the east (ie the user's right hand side) and thus substantially perpendicular to the shaft 6. It will be appreciated by those skilled in the art that the engine 2 is able to be used for a cultivator or any other appliance requiring an exhaust nozzle outlet facing in the same direction relative to its output shaft.

A second class of appliance is that represented by the line trimmer 21 illustrated in Figs. 4-6. The line trimmer is powered by an engine 22 and has two handles 26 and 23. A cutting line 24 is connected to the engine 22 by means of a shaft (not illustrated) which passes through the handle 26. In use the operator holds the handle 23 in the left hand, with the left arm substantially extended and the handle 26 in the right hand. If the operator of the trimmer 21 of Fig. 4 is regarded as facing north, the handle 26 lies approximately north and at the centre of an arc through which the cutting head 24 is reciprocated. Thus the engine shaft points to the north.

As seen in Fig. 5, the engine 22 is provided with the cowling 8 as before, however, as it apparent from Fig. 6 that the muffler 12 is provided with an exhaust nozzle outlet 14 which is directed away from the user (ie towards the south). The muffler 12 thereby directs its exhaust gases away from the user and in a direction opposite to that in which the engine shaft points. Further, the air heated by being passed over the engine cylinder is expelled to the east and south-east via the cowling 8. Unlike the arrangement of Fig. 2, in the arrangement of Figs. 4-6, the exhaust nozzle outlet 14 directs exhaust gasses through the exhaust nozzle aperture 9 of the cowling 8. It will be apparent to those skilled in the art that the engine 22 can also be used for a brush cutter.

Turning now to Figs. 7 and 8, here a blower appliance 40 has a handle 41, a high velocity air outlet 42, an air outlet tube 43 and an engine 2. The cowling 8 is illustrated in Fig. 7 but removed in Fig. 8 in order to illustrate the muffler 12 and its exhaust outlet 13. The engine 2 has its output shaft (not illustrated) connected to drive a rotary impeller (not illustrated) located within a housing 44. In addition, a curved deflector 45 is provided which deflects air past the cooling fins of the cylinder so as to exit via exit apertures 111 (Figs. 2 and 7). The deflector 45 is also visible in Fig. 3.

As best seen in Fig. 10, there are two possible positions (indicated at 141 and 142) for the operator depending upon whether the operator holds the handle 41 in the right or left hand respectively. This is independent of the usual writing hand of the operator since most operators will use either hand independently depending upon which hand happens to be tired.

If the operator is regarded as facing north in Fig. 10 (in both positions 141 and 142) then the direction in which high velocity air is blown by the appliance is north, the engine shaft (not illustrated) faces west, the exhaust outlet 13 (Fig. 8) faces north, and the heated air which passes over the cylinder is expelled in a north to north easterly direction indicated by arrows A in Fig. 10 which is a direction which is approximately at 45°-90° to both the crankshaft axis (arrows B). The exhaust nozzle direction is indicated by arrow C. Thus both the exhaust and the heated air are directed away from the operator positions 141 and 142. The engine shaft drives a rotary impellor (not illustrated) which is located within the housing 44. The situation may be summarised by the following Table 1. Table 1

In the above, the compass directions for ease of comprehension, have been provided with reference to the operator. However, if the output shaft direction is now taken as the reference direction, Table 1 above can be converted as follows:

Table 2

It follows from the above that the seemingly conflicting requirements of the three general categories of appliances, can be reduced to two categories of engine, and with a simple modification to the muffler, to a single engine platform. In particular, the engine 2 and the engine 22 are identical in all respects save for the direction in which the exhaust nozzle outlet 13, 14 of the muffler 12 faces. In particular, the one cowling 8 by virtue of its apertures 9, 10 and air slots 11 can be used for all three appliances.

Turning now to Figs. 11-14, in Figs. 11 and 12 the muffler 12 as used in Figs. 1-3 and Figs. 7 and 8 is illustrated whilst in Figs. 13 and 14 the muffler 12 as used in Figs. 4-6 is illustrated, it being apparent that the muffler 12 has a common muffler body 30 with two substantially identical exhaust nozzle mounts 31 and 32. Each exhaust nozzle mount 31, 32 takes the form of an exhaust opening 33 and two fastener receiving apertures 34. In Figs. 11 and 12, the exhaust nozzle mount 31 is closed by means of gasket 36 and cover 37 which is secured in place by means of fasteners 38. However, the exhaust nozzle mount 32 is open and receives a spark arrestor 39 formed from metal gauze together with a gasket 36 and an exhaust nozzle outlet 13, 14 all of which are secured in place by a means of fasteners 38. The spark arrestor gauze can alternatively be affixed to the end of the exhaust nozzle (not illustrated).

In Figs. 13 and 14, the arrangement is identical save that the cover 37 is placed over the exhaust nozzle mount 32 whilst the exhaust nozzle outlet 13, 14 is secured to the exhaust nozzle mount 31.

Figs. 15-18 illustrate a second embodiment of the muffler of Figs. 11-14. The muffler 212 of Figs. 15-18 has an exhaust nozzle mount 231 which takes the form of a flat annular area which surrounds a threaded aperture 236. The aperture 236 is dimensioned to receive either a plug 237 or a nozzle outlet 240 which is equipped with a gauze spark arrestor 239. Both the plug 237 and outlet 240 form a mating seal with the threaded aperture 236. In Fig. 15 the plug 237 and nozzle outlet 240 are shown in exploded fashion, and in Fig. 16 are shown installed. As illustrated in Figs 17 and 18, the positions of the plug 237 and nozzle outlet 240 can be exchanged to change the engine suitability of the muffler 212.

Turning now to Fig. 19, the cowling 8 is provided with a number, typically five, of spaced apart protruding fingers 301 which are integrally moulded into the cowling half 308, and which form a mating fit with a corresponding number of moulded recesses 302 in the other cowling half 318. In particular, the fingers 301 and recesses 302 are preferably arranged along thin edges where their inter-engagement provides an increase in the stiffness of the surface adjacent the edge.

Thus, although the two halves 308 and 318 of the cowling 8 are screwed together by means of threaded fasteners, the inter-engagement of the fingers 301 and recesses 302 provide a number of advantages. Firstly, the inter-engagement is sufficient to hold the two parts 308, 318 inter-engaged after they are initially pressed together during assembly. This assists in placing and tightening the threaded fastener(s). Secondly, fewer threaded fasteners are required because of the inter- engagement of the fingers 301 and recesses 302. Thirdly, as explained above the stiffness of the cowling 8 as a whole is improved. Fourthly, the fingers 301 and recesses 302 can be provided at low cost since the cowling halves 3085 318 can be fabricated using low cost "line of draw" male and female moulds. This is to be contrasted with moulds for conventional cowlings which use complicated side draws, and generally several of them, which can increase moulding costs by up to a factor of 3.

It will be apparent that the above described arrangement provides a number of very substantial advantages. In particular, only a single engine platform 2, 22 needs to be manufactured and that engine is able to be used either with the muffler 212 or with either the muffler 12 as illustrated in Fig. 11 or with the muffler 12 as illustrated in Fig. 13. However, in either event the same totality of parts for the engine platform are used, the only difference being the orientation of the exhaust outlet 13, 14 or nozzle outlet 240. In particular, the engine cowling 8 is the same irrespective of whether the engine is used in the form of engine 2 of Fig. 1 and Fig. 7 or engine 22 of Fig. 4. Furthermore, if demand for, say, the lawn edger 1 of Fig. 1 and/or the hand blower of Fig. 7 rapidly increases whilst the demand for the line trimmer 21 of Fig. 4 decreases, then it is a simple matter to convert the engine from the form 22 illustrated in Fig. 4 to the form 2 illustrated in Fig. 1 merely by changing over the arrangement of the exhaust outlet of the muffler 12 or 212. In this way greater flexibility of manufacturing and a reduction in the number of parts required to be held in stock, are able to be achieved. This is a substantial advantage in an age of globalisation where the engine manufacturer can be on one continent and the appliance manufacturer can be in another continent, both separated by a supply line including slow sea transport which is also made slower by recent security against terrorists. Thus the above described arrangements permit lead times to customers to be reduced notwithstanding changes in customer preference as to type of appliance.

The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. For example, other methods and/or mechanisms for releasably mounting the exhaust outlet 13, 14 to the muffler body 30 other than the use of fasteners 38 will be apparent to those skilled in the art. For example, a bayonet type releasable engagement can be used. Alternatively, the muffler manufacturer can produce two types of muffler with a nozzle outlet welded to the required exhaust nozzle mount. In this case the spark arrestor would be fitted to the free end of the exhaust nozzle. Then the required type of muffler is fitted to the otherwise common engine platform to create either engine 2 or engine 22 as desired.

The term "exhaust nozzle mount" as used herein is intended to embrace the fiat area which is able to circumscribe an exhaust opening 33 and to which an exhaust outlet 13, 14 or nozzle outlet 240 can be secured or releasably secured by any means.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of .