AU2005203380A1 - Manually powered lawn edger - Google Patents

Description

ci 0

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant: JOHN JENSZ Invention Title: MANUALLY POWERED LAWN EDGER The following statement is a full description of this invention, including the best method of performing it known to me: 2 O Manually Powered Lawn Edger 0g Field of the Invention SThe present invention relates to an apparatus for lawn edging.

5 Background of the Invention oDifferent types of devices have been used in order to provide neat lawn edging. The most simple of othese devices involves a cutting wheel with a horizontal 00 nfootrest which enables a person to push the wheel along a lawn edge and to use their foot to force the wheel along.

This type of device is very crude and requires a great o deal of exertion to operate it.

ci Other types of devices have also been devised but are either very expensive because they require motorisation or are difficult to use because they require a significant amount of physical exertion.

The present invention provides an alternative type of apparatus for lawn edging.

Summary of the Invention According to a first aspect of the present invention there is provided an apparatus for lawn edging comprising first and second spaced apart discs with their major faces substantially opposite each other and adapted to rotate at different speeds in substantially the same direction, each disc having a plurality of teeth whereby a tooth on one disc is adapted to cut grass when aligned with a tooth on the other disc in a cutting deposition.

It is preferred that a cutting deposition is when one tooth on one disc passes by another tooth on the other disc.

Preferably the cutting disposition is when cutting edges of opposing teeth at least partially overlap.

Preferably the cutting disposition is determined when opposing teeth contact each other.

It is preferred that opposing teeth on the discs are inclined toward each other.

R:1\SuoB\Keep\speci\p57493,spec.doc 27/07/OS 3 o Preferably a tooth at the lowermost edge of each 0g disc is adapted to be aligned in a cutting disposition.

SOne disc may have more teeth than the other.

Preferably substantially opposite includes anywhere between parallel and at 600 apart.

oIt is preferred that the disc which is adapted to rotate more quickly has the least number of teeth.

oPreferably the tooth number on each disc is 00 M dependent upon the turns ratio of one disc relative to the other multiplied by the angle factor, where the angle factor is the distance a disc rotates to complete a full Scutting operation.

The angle factor may be determined as the angular distance of the smallest tooth on either disc.

The cutting disposition preferably corresponds to the angle factor.

It is preferred that the cutting disposition corresponds to the period during which opposing teeth are in contact with each other.

Preferably the teeth number for a turn ratio of 5:4 and angle factor 8 is 40 and 32.

Preferably the teeth in the cutting disposition contacting each other have at least part of their cutting edge contacting the opposing face of the other.

Preferably contact between teeth occurs at the outer edge thereof.

The cutting edges may be self-sharpening.

Preferably the teeth in the cutting disposition are configured to be urged into contact with each other.

Preferably cutting occurs at the lowermost extremity of the opposed discs.

Teeth preferably are trapezoidal in shape with cutting edges on non-parallel sides of the trapezoid.

Preferably the cutting are on leading and trailing edges of opposing teeth.

According to one embodiment each disc is spaced apart on a common axle.

H:\SueB\Xeep\speci\pS46iepeedoc 26/01/05 4 O The common axle may be bent whereby the discs are 0 angled towards each other at a lower peripheral edge.

SThe discs may be closest together at their lowermost edges.

The discs may be parallel with their teeth angled otowards each other.

Preferably the common axle includes first and o second bent shafts at a substantially small offset angle 00 M with respect to each other.

It is preferred that the discs are spaced apart from each other and form an angle relative to each other, o which angle preferably corresponds to the difference in c orientation of the shafts on which they are located.

Preferably the angle is less than 10 degrees apart.

The angle of the shafts, the teeth size and the distance between the discs preferably controls the amount of contact area between teeth of the discs in the cutting disposition.

It is preferred that the cutting performance of the teeth is controlled by controlling the amount of pressure between contacting teeth during a cutting action while in a cutting disposition.

The teeth may be arranged on each disc whereby when a tooth of one disc is positioned at the lowermost point of the apparatus it overlaps an opposing tooth on the other disc at least partially.

The apparatus may include a support frame.

Preferably the support frame comprises an elongate shaft.

The support frame may include a lower frame section for supporting the or each axle on which the discs are supported.

The disc frame may be for supporting the discs.

The lower frame section may be configured to support a gear means which provides gearing between the first and second discs.

14:\SueE\Kecp\SpCC1\p5 7 .spc~ &c 26/Q7/C~5 5 o The gearing means may comprise a chain drive system or gear wheels.

The gearing means may be adapted to drive one ;disc at a slower speed than the other.

The gearing means may comprise an idler assembly including an idler housing and an idler shaft.

The gearing means may provide a plurality of sprockets.

M Preferably the gearing means comprises upper and o 10 lower sprocket sets.

The upper sprocket set may include a large and o small sprocket.

0g Preferably the gearing means includes a large and small sprocket which rotate together.

Preferably the large and small sprockets are fixed together and mounted at opposite ends of a hollow shaft.

It is preferred that the large and small sprockets are mounted on an idler shaft housing which is mounted on an idler shaft.

Preferably the lower sprocket set comprises substantially identical sprockets mounted on a common shaft.

It is preferred that each of the lower sprockets rotate independently of each other.

The upper and lower sprocket sets may be aligned to permit first and second chains respectively to be mounted thereon between left upper and lower sprockets and right upper and lower sprockets.

The lower sprockets may be mounted on a bent axle.

The bent axle preferably tapers on either side of a central portion.

The discs may be mounted respectively on either side of the central portion.

The discs are preferably each mounted on shaft housings which are rotatably mounted on bearings on the H:\SueE\Keep\speci\pS743 spe-doc 26/03/05 6 o bent axle.

0 The discs may be located inside the left and o right side sprockets of the sprocket pair.

Preferably the gearing means includes a plurality of sprockets in a set.

o It is preferred that the lower frame section comprises parallel vertical side walls and an upper flat o horizontal wall.

00 M It is preferred that the apparatus includes a chain adjustment means.

1 It is preferred that the distance between the sprocket sets can be varied by a control means.

ci The control means preferably comprises frame support members through which the idler shaft is mounted.

Preferably the frame support members comprise elongate members which are able to move up or down by an adjustment means.

The upper sprocket set preferably comprises left and right side sprockets mounted on a shaft extending between the vertical side walls of the upper end of the lower frame section.

It is preferred that the frame support comprises an upper frame section.

Preferably the frame support comprises an elongate member.

The elongate member preferably has handle bars at a top end thereof.

It is preferred that the elongate member is telescopically adjustable.

Preferably the chain extends between upper and lower sprocket sets of the left and right side respectively.

A gearing system preferably controls the number of turns one disc makes relative to the other disc regardless of which disc is the driving side.

It is preferred that the turns ratio for left and right is determined in accordance with the preferred R:;\SueB\Xeep~speci\pF7 4;3.-qpec-doc 2(707/05 7 o embodiment.

0g It is preferred that the disc teeth numbers are 0 dependent on their relative speed of rotation.

Preferably the larger sprocket of the upper sprocket set is on the same side as the disc with the olesser number of teeth.

Preferably the disc with the most teeth has a 1:1 gearing ratio with the smaller sprocket on the idler 00 Mn shaft.

o 10 Preferably the turns ratio is 4 is to According to one embodiment the lower sprocket o set has substantially the same gearing ratio.

0g It is preferred that the disc with the least number of teeth is located on the same side of the apparatus as the larger sprocket of the idler assembly.

It is preferred that the drive chain extends between the left side of the upper and lower sprocket set, i.e. the smallest sprockets of each sprocket set.

The lower sprocket set may be smaller to allow greater clearance for chains to the ground or to the periphery of the discs.

The alignment of the teeth on each disc is preferably adjustable by aligning disc teeth prior to fitting both chains on sprockets.

The torque applied in a cutting action can be varied by varying the ratio of turns ratio between discs.

According to another aspect of the present invention there is provided an apparatus for edging lawns comprising first and second discs each having a plurality of cutting teeth, a frame connected to the discs and a gearing means which permits one disc to move at a different speed to the other in the same direction of rotation as the apparatus is pushed in one direction.

Preferably the discs are aligned with their major faces substantially opposite.

Discs may be aligned in substantially parallel planes or in angular offset planes.

E: \SueB\Keep\apecl\pS,'743.spec.doc 2107/105 8 The discs may be configured so their lower 0peripheral edges converge. The discs may be configured so tthey diverge upwardly.

;The discs may be mounted on shafts which are linearly offset with respect to each other.

o It is preferred that the discs are located on different ends of a bent axle.

o The bent axle may be symmetrical about a central 00 e portion.

M 10 The central portion preferably comprises a boss 0 or collar.

o The frame and gearing means preferably have at Sleast one of the above recited features.

According to another aspect of the present invention there is provided a gearing assembly for a lawn edger comprising a first sprocket set, a second sprocket set, a chain means comprising at least one chain connecting the first and second drive sprocket sets wherein one of the sprocket sets is adapted to be connected to discs for cutting grass and wherein the first sprocket set includes an idler assembly comprising left and right side sprockets which are fixed together for rotation and the second sprocket set comprises left and right side sprockets which are able to rotate independently of each other.

The first sprocket set may be supported on a housing which supports the sprockets and is rotatable on a common shaft.

Preferably the first sprocket set is supported on an idler assembly.

The second sprocket set may comprise a drive assembly attachable to the discs for cutting.

Alternatively the above is reversed.

The sprockets in the first sprocket set may have different sizes.

The sprockets in the second sprocket set may be mounted on shafts which are not co-linear.

H: \S.IaB\Keep\speci\p l48 3.spec.doc 26/07105 9 O Preferably the shafts are part of a common bent 0 axle.

0Preferably the chain means includes the chain extending between first and second sprocket sets on a left side of the apparatus and one chain extending between ofirst and second sprocket sets on a right side of the apparatus.

oAccording to an alternative embodiment multiple 00 M sprockets and chains are provided.

Brief Description of the Drawings C Figure 1 shows a perspective view of an apparatus ofor cutting lawn according to a preferred embodiment of C the present invention; Figure 2 shows a lower section of the apparatus with the handle removed; Figure 3 shows a perspective side view of the lower section of the apparatus with the gearing assembly cover removed; Figure 4 shows a side view of the lower section of the assembly shown in Figure 3; Figure 5 shows a front view of the lower section of the apparatus excluding the cover; Figure 6 shows a perspective side view of the gearing assembly; Figure 7 shows a front sectional view of the gearing assembly; Figure 8 shows a side view of the gearing assembly; Figure 9 shows a front sectional view of drive sprocket set of the gear assembly shown in Figures 6 to 8; Figure 10 shows a side view of a sprocket of the drive sprocket set shown in Figure 9; Figure 11 shows a cross-sectional view of an idler sprocket assembly of the gear assembly shown in Figures 6 to 8; Figure 12 shows a side view of the idler sprocket assembly; IH~SUeB'Xee\.peci p?63.lpcdc 160~n 10 o Figure 13 shows a perspective view of the idler 0 sprockets and idler housing of the idler sprocket Sassembly; Figure 14 shows a top view of the idler sprockets 5 and idler housing; oFigure 15 shows a front view of the frame housing for the gear assembly; and oFigure 16 shows a close-up of cutting teeth on a 00 M cutter blade of a preferred embodiment of the invention.

o 10 Detailed Description of the Drawings c As shown in Figure 1 the apparatus consists of o handle bars 11 mounted on a telescopically adjustable ci supporting rod 12. At the lower end of the rod 12 a lower frame section 13 is mounted thereto through a connecting socket 14.

The lower frame section 13 shown more clearly in Figure 2 consists of a gear assembly cover 15, a disc cutter cover 6 and a pair of cutting discs (blades) 16 and 17, typically circular metal plates.

As shown in Figure 5 there is a left side-cutting disc 16 and a right side cutting disc 17. The cutting discs are mounted on a lower shaft 18 inside left and right side vertical walls 19, 20 of frame support 21. The frame support shown more clearly in Figure 15 is typically made from plate steel which is either bent or welded to form an upper flat section 22 which as shown is in a typically horizontal disposition when the apparatus is shown in a vertical orientation. The side wall sections 19 and 20 extend downwardly on each side of the flat plate 22 and are provided with upper and lower aligned holes for an idler shaft 23 and a drive axle 24.

As shown in Figure 15 the idler shaft 23 is typically held in place by bolts 25 and the drive axle 24 by bolts 26 which are respectively screwed into either end of the shaft and axle respectively.

The drive axle 24 is also characterised by having a central collar 27 which divides the axle into left and H:\SueB\Keep\speci\p57463.5pec.doc 26/07/05 11 o right side bent shafts 28 and 29 respectively.

0 Each of the shafts 28 and 29 deviate typically by tonly a few degrees from being co-linear or horizontal as shown in Figure 15. It is preferred that both shafts have the same offset angle with respect to the collar 27 or a ohorizontal axis. The degree of offset determines the angular displacement between the cutter discs mounted on othe shafts.

00 n If the central collar 27 or boss is on a horizontal axis, each shaft 28 and 29 would have an angle C downwardly of between 0.50 and 10 each side. This gives an oincluded angle of between 1780 and 1790. The actual figure 0 depends upon the thickness of the cutters and their composition (flexibility) and the diameter.

The distance separating the cutter blades is controlled by the width of the central collar. As the cutter blades are pushed onto each side shaft they first make contact at their lower edges. At this point the bottom edges are just touching. The upper edges are then say 10mm apart. At the centre the gap is approximately The cutter discs are then pushed together until the inner bearings contact the central collar with the gap between the cutter discs at the centre being 2 to 3mm.

Preferably the aim is to flex the outer edges of the cutter blades where they make contact so that they are parallel and have the required pressure between them.

Returning to Figure 5 the cutter discs 16 and 17 can be shown converging at their lowest extremities 30, 31 so that their teeth are in contact. At their upper extremities 32, 33 the spacing between them is greatest.

Each of the cutter discs 16, 17 is connected to left and right side sprockets 34, 35 which are shown more clearly in Figure 9. Thus each of the cutter discs 16, 17 is mounted to a cutter housing 36, 37 which is mounted on bearings on the cutter shafts 28, 29. The drive sprockets 34 and 35 are mounted on the cutter housings 36, 37 and connected thereto by four symmetrically placed bolts 38, H:\S~eB\Keep\spec\p57183,spec.doc 2 /07/Q5 12 o 39 respectively. Chains 40 and 41 respectively are 0 located on the sprockets 34 and 35 and extend upwardly to on left and right side sprockets 42, 43 of the idler assembly ;Z 44.

As shown in Figure 11 the idler assembly 44 o consists of an idler sprocket set 42, 43 and idler housing which is mounted on bearings 46 on the idler shaft 23.

o The right side sprocket 43 has a larger diameter than the 00 Mn left side sprocket 42. Both sprockets 42, 43 are bolted together by bolts 46.

Cl The length of the chains 40 and 41 is dependent oupon the size of the sprockets and the distance between 0 the upper and lower sprocket sets, which in this case are the idler and drive sprocket sets. The distance between these sets however can be varied as the idler sprocket set is mounted on the idler shaft 23 which extends through vertical slots 47 in each of the vertical walls of the frame support 21. As shown in Figure 15 the ends of the shaft 23 abut against vertical plates 48, 49 which have circular holes to allow insertion of the bolts therethrough.

Upper ends of the vertical plates 48, 49 are provided with lateral detents or lugs 50, 51 which are welded to, formed or abut with vertical cylindrical rods 52, 53 respectively. These rods have an external thread which allows tightening nuts 54, 55 to move the rods 52, 53 up or down by clockwise or anticlockwise rotation. In this manner it is possible to move the idler assembly up or down, by moving the idler shaft 23 up or down within the slots 47 and tightening or loosening bolts 25, as required.

As shown most clearly in Figure 3 the cutter blades 16, 17 have a series of teeth 60, 61 provided around their peripheral edge. Teeth are typically planar with the major faces of each cutter disc and have a trapezoidal shape, with sharpened leading or trailing edges. The number of teeth on each of the cutter discs H:\SueB\t{oepX~peci\pFfl~3- ~pecdnc 2C/O7/65 13 o 16, 17 can be varied to optimise performance of the 0 cutting action provided when the apparatus is wheeled over the edge of a lawn. For example the number of teeth ;Z provided on each cutter disc is dependent upon the diameter of each disc. Typically the larger the diameter o of the disc the more teeth required.

The preferred diameter of the cutter discs 16, 17 o is between 250mm and 300mm. With these dimensions the 00 Mn cutter discs have enough clearance between ground and chain covers and thus avoids the need of a depth wheel, thus greatly improving manoeuverability.

o With larger diameter cutting discs the edger is cisupported better on soft ground. However if the diameter is too large it makes the edger bulky and expensive to build.

The preferred pitch of cutting teeth is between and 30mm. If the cutting teeth have a greater pitch then too much grass is presented to each cut. If less than 20mm pitch is used the teeth occupy too much space to allow the grass easily between them.

The size or profile of a tooth is determined by the tip at 6mm and the angle between leading and trailing edges Two examples are set out below for a cutting disc diameter of 280mm and 250mm respectively; Example 1 For a cutting disc diameter of 280mm this gives a circumference of 880mm. At 30mm pitch (the maximum distance) this gives 30 teeth as the minimum number of teeth. At 20mm pitch (the minimum distance) gives 44 teeth as the maximum number of teeth. Using 5 to 6 turns ratio both these numbers have to be multiplied by a common number (angle factor) to give tooth numbers between 30 and 44. In this example there are two options. An angle factor of 7 giving 7 X 5 35 teeth on the faster rotating cutter blade and 7 X 6 42 teeth on the slower rotating cutter disc, or an angle factor of 6 giving 6 X 5 H;\SueE\Keep\spec:\pE 748.speo.doc 26/07/05 14 o teeth on the faster rotating cutter disc and 6 X 6 36 0 teeth on the slower rotating cutter disc. In both options 00 the tooth numbers fall within the limits of this diameter ;Z and 44. It should be noted that in each case the angle factor number is how many times the full cutting sequence o is repeated around the circumference.

Example 2 o Cutting disc diameter 250mm 785mm 00 Mn circumference. At 30mm pitch (the maximum distance) this gives 26 as the minimum number of teeth. At 20mm pitch (the minimum distance gives 40 as the maximum number of o teeth). Using a 4:5 turns ratio there are two options; an 0 angle factor of 8 giving 8 X 5 40 teeth on the slower rotating cutter disc and 4 X 8 32 teeth on the faster rotating cutter disc, or an angle factor of 7 giving 7 X 35 teeth on the slower turning cutter disc and 7 X 4= 28 teeth on the faster turning cutter disc. Using a 5:6 turns ratio at this diameter there is only one option that meets parameters. This is an angle factor of 6 giving 6 X 6 36 for the slower turning cutter disc and 6 XC 5 teeth for the faster turning cutter disc. In both of these instances tooth numbers fall within the limits for this diameter, that is 26 and 40. It should be noted the turns ratio number for one cutter disc is the number of teeth in a cutting sequence for the other cutter and vice versa.

A decision on which combination of diameter, turns ratio and angle factor to use is arbitrary. For example two models could be used, one using higher torque and larger diameters for commercial use and another using less torque and smaller diameters for private use.

The turns ratio is also relevant when determining the optimum number of teeth for each cutter disc. The turns ratio is determined by the relative speed of rotation of one cutter disc compared to the other. This is controlled by the gear assembly 18. In addition the H:\Sve\Xeep\sp~cA\p574S2Stpec.doc 2C/07/ORS 15 o teeth numbers are dependent upon the angle factor which is 04 the distance the discs rotate in order to complete a full b cutting action. Thus wider teeth will give a greater angle factor. The angle factor may be converted from an 5 angle of 3600 if it is divided into 3600 to give the odistance the discs rotate to complete a full cutting sequence. In effect the cutting area between discs is the osame as the angle factor. The cutting area and cutting 00 M sequence have to coincide to provide the best cutting action.

oIdeally teeth on each disc are the same.

oIt is preferred that a turn ratio of 5:4 X 8 ci angle factor is provided. The cutter disc which rotates fastest preferably has the least number of teeth.

Therefore in this example this would be 4 X 8 which equals 32 teeth. The other cutter disc which turns slower has more teeth and a number of teeth which is determined by X 8 which is 40 teeth.

As the apparatus is pushed over the ground the same number of teeth on each cutter disc passes a given cutting point.

This ensures that cuts are finished at the same place. Thus if the apparatus is used in a completely vertical orientation the cut takes place at the very bottom of the apparatus when the opposing teeth of each cutter disc are overlapping. However by tilting the apparatus the position where the cut finishes changes in relation to the ground. This is because the overlapping teeth, which are normally positioned square to the ground, are tilted and are therefore cutting at more of an angle with respect to the vegetation they are cutting. If the apparatus is titled a long way back then the teeth tend to cut at a greater and greater angle so that they are coming up from underneath a blade of grass for example and lifting it upwardly in addition to moving forward.

Another factor in the cutting action is the angle at which one cutter disc is disposed with respect to the other. In H: \SueD\<eep\speci\p5 7 483 .spaC.doc 26/07/05 16 o addition the space between the discs is also a factor.

0 Thus the angle of the shafts and the distance the cutter 0 discs are apart controls the amount of contact between the ;discs. For convenience this is called the angle factor.

Thus for an angle factor of 8 there is 450 of contact. The o thickness and type of metal used in cutting discs also controls the amount of pressure between them for a chosen o contact area. It is desirable to obtain the correct 00 M pressure between cutters to prevent cutters being forced apart when cutting tough material. The pressure also controls the rate of self-sharpening. By loosening o mounting bolts and rotating shaft it is possible to alter 0 the position of the contact area in relation to the frame of the apparatus.

Typically the discs will have inherent resilience so that teeth which contact each other under a degree of pressure determined by the design parameters outlined above, to allow flexibility between the teeth particularly when different types of material are being cut or stones are accidentally caught between the cutting teeth.

According to one embodiment the trailing edge of teeth on one cutter blade normally being the slower cutter blade perform a cutting action with the leading edge of teeth on the faster cutter disc.

The gearing assembly has a number of parameters that can be varied in order to alter characteristics of the apparatus. These include the size of the sprockets, the distance between sprocket sets, the number of sprocket sets, the number and type of chain etc.

The gearing assembly effectively controls the number of turns one cutter disc makes in relation to the other regardless of which side is the driving side. For .convenience the preferred turns ratio is set out below in whole numbers, for example 4 is to 5. Thus the ratio of the large right side sprocket 43 of the idler assembly when compared to the diameter of the left side sprocket 42 provides a gearing ratio of 4 is to H:\SueB\Keep\spec1\pS7413.-pec.dC 2O/OE 17 o The left and right side sprockets 34, 35 of the C drive sprocket assembly are effectively identical and rotate independently on their respective shafts 28, 29.

Thus in operation when the apparatus is pushed over the ground surface the chain 40 which extends around and o between the left side sprockets of the idler and drive sprocket assemblies rotates more quickly than the right 0side chain 41. The results are that the left side cutter 00 M disc 16 moves more quickly than the right side cutter disc 17. Accordingly the number of teeth on the left side disc c is lower than that on the right side disc.

oFor the example of a 4:5 ratio, 5 turns of the Ci left cutter disc 16 results in 4 turns of the right cutter disc 17 with both cutter discs moving in the same direction of rotation. The consequence of this characteristic is an increase in torque between the cutter blades. For every 5 turns the right cutter disc rolls over the ground, the left side cutter disc 16 turns 4 times. This results in a torque increase of over 400% between the cutters. Therefore the apparatus is easily pushed through tough grass and small branches and palm frond leaves. The smaller the turns ratio the greater the torque which is able to be generated. This is in contrast to the situation where the cutter discs rotate in opposite directions.

Set out below is an example of how the change in turns ratios results in changes of numbers of teeth and resultant torque between cutter discs.

A number of turns ratios are as No. of Torque follows teeth increase 1 to 2 Low torque large 12 to 24 100% difference in tooth numbers between sprockets 2 to 3 16 to 24 200% 3 to 4 15 to 20 300% 4 to 5, preferred ratio for 16 to 20 400% H:\SueB\Rccp\tpeci\p57Et.peC.doc 26/101/05 18 o current model C 5 to 6, preferred ratio for 20 to 24 500% larger diameter cutters 6 to 7, high torque small 24 to 28 600% difference in tooth numbers o between sprockets o If the torque increases above 600%, i.e. the 00 n turns ratio is above 6:7, this high ratio of torque obetween cutting edges exposes them to damage if foreign material is encountered.

oIt is preferred that the sprocket tooth numbers C are arranged so that both chains can be adjusted simultaneously. Therefore to change the position that cuts finish in the left side chain 40 can be removed and the cutter discs rotated until teeth align as desired.

The chain can then be refitted.

By having the correct number of teeth on each cutter disc, it is possible to ensure that each cut between opposing teeth on the cutter discs finishes in the same position in relation to the frame.

Figure 16 shows a close up view of offsetting of the teeth on each of the cutter blades.

The offset is towards the opposing teeth of the other cutter blade. It is preferred that it is substantially parallel to the cutting disk. In one embodiment the tooth offset is 2mm.

There are two advantages in having offset teeth.

One is that the only contact between the two cutter blades is at the cutting edges of the teeth and it is more difficult for material to roll between cutters forcing them apart for a given amount of pressure between the cutter discs. In addition self-sharpening does not work effectively when the cutting teeth are flat and in line with the disc. With the offset cutting edges the wear is better controlled and in the right area. As shown in figure 1 reference numeral 100 points to a shiny strip of H: \SucB\Kccp\pec\p5 7 83.specdoc 2C/(,t/R 19 o each tooth just behind the cutting edge.

0 It should be noted that the representation shown in Figure 16 is of the inside of one cutter blade.

Thus two cutter blades of the type shown in 5 Figure 16 would have the offset teeth facing each other.

oThus from the above it can be seen that it is possible to design the apparatus so that whenever a tooth is located at ground level it is at least partially 0C M overlapping an opposing tooth on the opposing cutter disc.

It is preferred that the smallest sprocket set is located on the cutter disc end of the apparatus to give the most clearance of chain guards to ground and kerbing C or vertical walls. The other side cutter with the most teeth preferably has a 1:1 gearing with the idler assembly and has the same sprocket on both cutter and idler.

Although the above apparatus has been described having regard to a gearing system utilising sprockets and chains, it is also possible to use other gearing systems without chains. For example a planetary gearing assembly might be utilised.

With the above-described apparatus the height of the handlebars can be adjusted and the tilt of operation can be changed as desired. Furthermore because the cutter discs rotate in the same direction there is a torque multiplication effect which assists a cutting action.

According to one version of the invention the gear ratio of 3:4 is used to lower the cost in manufacturing. Smaller sprockets may also be used outside of the cutter disks to give more ground clearance.

According to one embodiment a ratio of provides an advantage in tough conditions.

With regard to manufacturing of the cutting teeth it is preferred that they are made in a number of segments and may be secured around the perimeter of the disks.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part H:XSueB\KeeptSpeci\p57463.spec.doc 26/071/05 20 o of the common general knowledge in the art, in Australia Sor in any other country.

In the claims which follow and in the preceding Sdescription of the invention, except where the context requires otherwise due to express language or necessary o implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, o i.e. to specify the presence of the stated features but 00 C not to preclude the presence or addition of further 0 features in various embodiments of the invention.

o 10 features in various embodiments of the invention.

rcl T-LSucE\Kccp5pct\pS74E3Bptcc~dOC 2/J /U

Claims (29)

1. 3. The apparatus as claimed in claim 1 wherein C a tooth at the lowermost edge of each disk is adapted to be aligned in a cutting disposition.
2. 4. The apparatus as claimed in claim 3 wherein the teeth at the lowermost edge of each disk are adapted to be aligned in a cutting disposition in which the teeth are urged into contact with each other. The apparatus as claimed in claim 1 wherein teeth are trapezoidal in shape with cutting edges on non- parallel sides of the trapezoid.
3. 6. The apparatus as claimed in claim 1 wherein each disk is spaced apart on a common axle.
4. 7. The apparatus as claimed in claim 6 wherein the common axle is bent whereby the disks are angled towards each other at a lower peripheral edge.
5. 8. The apparatus as claimed in claim 7 wherein the common axle includes first and second bent shafts at a substantially small offset angle with respect to each other.
6. 9. The apparatus as claimed in claim 8 wherein the disks are spaced apart from each other and form an angle relative to each other, which angle corresponds to the difference in orientation of the shafts on which they are located, the angle being less than 100 apart. The apparatus as claimed in claim 1 wherein teeth are arranged on each disk whereby when a tooth of Fi:\SueB\Kcep\speci\p5'483,spec-doc 27/07/65 22 o one disk is positioned at the lowermost point of the 0 apparatus it overlaps an opposing tooth on the other disk at least partially.
7. 11. The apparatus as claimed in any one of the 5 preceding claims including a support frame comprising an o elongate shaft.
8. 12. The apparatus as claimed in claim 11 o wherein the support frame includes a lower frame section 00 M for supporting the or each axle on which the disks are supported.
9. 13. The apparatus as claimed in claim 12 owherein the lower frame section is configured to support a C gear means which provides gearing between the first and second disks.
10. 14. The apparatus as claimed in claim 13 wherein the gearing means comprises a chain drive system. The apparatus as claimed in claim 13 wherein the gearing means is adapted to drive one disk at a slower speed than the other.
11. 16. The apparatus as claimed in claim 13 wherein the gearing means comprises an idler assembly including an idler housing and idler shaft.
12. 17. The apparatus as claimed in claim 16 wherein the gearing means comprises upper and lower sprocket sets.
13. 18. The apparatus as claimed in claim 17 wherein the upper sprocket set includes a large and small sprocket which rotate together and are fixed together and mounted at opposite ends of a hollow shaft.
14. 19. The apparatus as claimed in claim 18 wherein the large and small sprockets are mounted on an idler shaft housing which is mounted on an idler shaft. The apparatus as claimed in claim 19 wherein the lower sprocket set comprises substantially identical sprockets mounted on a common shaft.
15. 21. The apparatus as claimed in claim wherein each of the lower sprockets rotate independently \SueD\Keep\Speci\p57463.pc.dDoc 21/01/05 23 o of each other.
16. 22. The apparatus as claimed in claim 21 Swherein the upper and lower sprocket sets are aligned to ;permit first and second chains respectively to be mounted 5 thereon between left upper and lower sprockets and right oupper and lower sprockets.
17. 23. The apparatus as claimed in claim 22 owherein the lower sprockets are mounted on a bent axle. 00 M 24. The apparatus as claimed in claim 23 wherein the bent axle tapers on either side of a central portion. o 25. The apparatus as claimed in claim 24 c wherein the disks are mounted respectively on either side of the central portion.
18. 26. The apparatus as claimed in claim wherein the disks are each mounted on shaft housings which are rotatably mounted on bearings on the bent axle.
19. 27. The apparatus as claimed in claim 26 wherein the disks are located inside the left and right side sprockets of the sprocket pair.
20. 28. The apparatus as claimed in claim 27 wherein the gearing means includes a plurality of sprockets in a set.
21. 29. The apparatus as claimed in claim 28 wherein the distance between the sprocket sets can be varied by a control means. The apparatus as claimed in claim 29 wherein the control means comprises frame support members through which the idler shaft is mounted and the frame support members comprise elongate members which are able to move up or down by an adjustment means.
22. 31. The apparatus as claimed in claim wherein the chain extends between upper and lower sprocket sets of the left and right side respectively.
23. 32. The apparatus as claimed in claim 1 including the gearing system which controls the number of turns one disk makes relative to the other disk regardless H:\SueB\Heep\speci\p57463.specdoc 27/07/05 -24 o of which disk is the driving side. ci 33. The apparatus as claimed in claim 32 wherein the larger sprocket of the upper sprocket set is ;Z on the same side as the disk with the lesser number of teeth and the disk with the most teeth has a 1:1 ratio o with the smallest sprocket on the idler shaft.
24. 34. An apparatus for edging lawns comprising 0 M teeth, a frame connected to the disks and a gearing means which permits one disk to move at a different speed to the ~fl other in the sane direction of rotation, as the apparatus is pushed in one direction. The apparatus as claimed in claim 34 wherein the disks are aligned with their major faces substantially opposite-
25. 36. The apparatus as claimed in claim wherein disks are configured so their lower peripheral edges converge.
26. 37. The apparatus as claimed in claim 36 wherein disks are mounted on shafts which are linearly offset with respect to each other.
27. 38. The apparatus as claimed in claim 37 wherein the disks are located on different ends of the bent axle which is symmetrical about a central portion.
28. 39. A gearing assembly for a lawn edger comprising a first sprocket set, a second sprocket set, a chain means comprising at least one chain connecting the first and second drive sprocket sets, wherein one of the sprocket sets is adapted to be connected to disks for cutting grass and wherein the first sprocket set includes an idler assembly comprising left and right side sprockets which are fixed together for rotation and the second sprocket set comprises left and right side sprockets which are able to rotate independently of each other.
29. 40. The apparatus as claimed in claim 39 wherein the first sprocket set is supported on a housing which supports the sprockets and is rotatable on a common H:\SueB he.Ap\s(jeCi\p574 j3.spec.doc 27/07/0L 25 o shaft. Cl 41. The apparatus as claimed in claim Swherein the first sprocket set is supported on an idler assembly. 5 42. The apparatus as claimed in claim 41 o wherein the second sprocket set comprises a drive assembly attachable to the disks for cutting. o 43. An apparatus substantially as hereinbefore CM described with reference to the accompanying drawings. C( X:\ueB\Kep\pecipS7463.pc.doc 2Cl':l/o