WO1990014755A1

WO1990014755A1 - Cutting blade and mounting

Info

Publication number: WO1990014755A1
Application number: PCT/AU1990/000236
Authority: WO
Inventors: William Henry Clarke
Original assignee: William Henry Clarke
Priority date: 1989-06-01
Filing date: 1990-06-01
Publication date: 1990-12-13

Abstract

A cutting blade (10) for a lawn mower and being formed from a resilient plastics material. The cutting blade (10) has a mounting portion (11) which is apertured (13) to permit its pivotal connection to a blade carrier (8). The blade has a cutting edge (14) formed along one elongate edge thereof and flow interference means such as ribs (16) vanes or upstanding projections on the upper surface of the blade. The blade may be formed with air flow control means such as an upturned flight (15) along its trailing edge. Retaining apparatus suitable for attaching an apertured member (10) to an apertured carrier (8) is also described. The retaining apparatus includes a base portion (44) adapted for retention by the apertured member (10), a retaining pin (37) adapted for passage through the apertured member (10) and the apertured carrier (8) so as to locate one relative to the other, the pin having a necked portion (38) which may be exposed at the side of te carrier remote from the apertured member (10), and a retaining clip (46) engageable with said necked portion.

Description

This invention relates to cutting apparatus and to retaining apparatus suitable for use therewith.

This invention has particular but not exclusive application to cutting blade assemblies for rotary lawnmowers, brushcutters and the like and for illustrative purposes reference will be made to such application. However it is to be understood that this invention could be used in other applications, such as edge-trimmers and industrial cutting apparatus.

Rotary lawnmowers are convenient and simple devices capable of handling a wide range of grass conditions. A particular advantage of such mowers is that short blades attached to a central support plate may be used. These blades may be replaced when worn by unbolting them from the central support plate and bolting replacements into position. Difficulty is often experienced during blade replacement due to the confined space in which the work is performed and to wear and corrosion of the mounting bolts, and this often leads to injury to the hands of the replacer.

Blades are typically made of high-carbon steel and this results in blades which are relatively brittle and which may break upon striking a hard object, with consequent risk of injury from the free portion of the blade. Additionally,, the blades must be formed by cutting and bending from steel strip, resulting in a blade shape which is not optimal for cutting or for generating the air flow necessary for grass discharge and or catching.

An alternative design of rotary lawnmower utilises a cutting bar the centre of which is attached to the cutter shaft and the ends of which form the cutting bars. In this case, worn blades necessitate the removal and replacement of the entire cutting bar with similar problems in respect of bolts as discussed above and with substantial material wastage. Similar problems also occur with brushcutters and the like using one-piece plastics material cutting discs with extended blades formed therein. The loss of a blade due to

SUBSTITUTESHEET breakage requires replacement of the complete cutting disc.

The present invention aims to alleviate the above disadvantages and to provide cutting apparatus which will be reliable and efficient in use. Other objects and advantages of this invention will hereinafter become apparent.

With the foregoing and other objects in view, this invention in one aspect resides broadly in a cutting blade for a lawn mower or the like, the cutting blade being formed from a resilient plastics material and including:- a mounting portion having attachment means for connection to a blade carrier; a cutting portion having a cutting edge formed along one elongate edge thereof; and flow interference means on the upper surface of the cutting portion. Preferably the flow interference means act to reduce the circumferential component of motion of cut grass within a mower's cutter housing and increase the radial component of motion of cut grass to assist its discharge from the mower's cutter housing. It is also preferred that the blade has air flow control means formed along its trailing edge for generating lift in an airstream flowing over the blade.

The plastics material is suitably a high-impact-strength material and the attachment means includes a circular mounting aperture formed through the blade such that it may be fastened to an aperture formed within a carrier. Of course the attachment means may include an integral mounting boss or stud formed thereon and adapted for engagement with a carrier aperture. Alternatively the mounting boss may be formed as a.separate fastener adapted to pass through the mounting apesrture and the carrier aperture and if desired it may be constituted by the shank of a bolt. The mounting boss may be formed with elastically-deformable retaining means, such as retaining lugs, whereby the mounting boss may be attached to the carrier by means of a snap-on connection. screwdrivers. The separate fastener may be in the form of retaining apparatus as hereinafter described.

The cutting portion may be substantially constant cross- section but preferably it is thicker adjacent the cutting edge. The thickened portion suitably has a transverse extent which increases away from the mounting portion. The flow interference means may be a plurality of separate upstanding projections on the upper surface of the cutting portion or it may be constituted by a series of upstanding ribs extending along the blade or along and across the blade. The ribs may also extend along an inclined flight at the trailing edge of the blade and forming the air flow control means.

If desired the ribs may be curved and may take the form of throwing vanes formed on the upper surface of the cutting portion. The blade carrier is suitably the cutter disc or bar of a rotary mower or it may be a carrier adapted for mounting on a brushcutter.

In a further aspect, this invention resides broadly in retaining apparatus suitable for attaching an apertured member to an apertured carrier, the retaining apparatus including:- a base portion adapted for retention by the apertured member; a retaining pin adapted for passage through the apertured member and the apertured carrier so as to locate one relative to the other, the pin having a necked portion which, in use is exposed at the side of the carrier remote from the apertured member, and a retaining clip engageable with the necked portion.

The necked portion may be reduced in thickness relative to the pin or it may be a portion of the pin separated therefrom by a collar or the like. Preferably, the retaining pin and/or the retaining clip are formed from a high-impact- strength plastics material, such as POLYCARBONATE plastics material, although other materials such as steel or other metals may be used if desired.

The pin may include a locking shank adjacent the necked portion and which cooperates with a retainer to prevent retraction of the pin through the apertured member and carrier. The retainer may be in the form of a spacer which may de displaced axially along the shank to clip into position or it may be in the form of a nut engageable with a thread or cam portion on the locking shank. In a preferred embodiment, the locking shank includes a locking groove or rib which engages with a complementary rib or groove formed in the bore of the spacer. The spacer or nut may include elastically deformable retention means, such as upstanding retaining lugs, whereby it may be attached to or interlock with the retaining clip. Alternatively, the spacer may also include clip holding means in which a holder on the retaining clip may engage to prevent disengagement of the clip from the neck portion. Suitably the holding means includes a recess formed in the upper face of the spacer and the holder includes elastically-deformable lug or lugs formed on the retaining clip. Of course, other clip locking means such as a lug formed on the locking collar and a recess formed on the retaining clip may be used if desired. Furthermore the holders on the retaining clip may engage with holding means formed directly in the carrier.

The air flow control means may include a portion of the blade formed into an aerofoil cross-section, and/or inclined at an angle to the direction of motion and the longitudinal axis of the blade. Alternatively, the blade may be formed with a longitudinal flange along the trailing edge of the cutting portion. The flange may be formed of a thickness just adequate to minimise deflections thereof due to the aerodynamic forces applied thereto, ensuring that the flange may deflect when subjected to unusual loads, such as hitting a loose stone or the foot of a user.

In yet another aspect, this invention resides broadly in including:- a support bar having a central mounting portion adapted for mounting to a drive shaft and blade mounting portions at opposed ends thereof adapted for supporting respective cutting blades, the blades being as described above and/or being connected to the bar by retaining apparatus as described above.

In order that this invention may be more easily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:-

FIG. 1 is a cutaway view illustrating a typical application of the present invention; FIG. 2 is a plan view of a preferred form of mower blade according to the invention;

FIG. 3 is an inverted plan view of the mower blade;

FIG. 4 is a side view of the mower blade and the associated retaining apparatus; FIG. 5 is an end view of the mower blade;

FIG. 6 is an enlarged perspective view of the retaining assembly illustrated in FIG. 4;

FIG. 7 illustrates an alternate form of clip which may be used with the retaining apparatus; FIG. 8 illustrates a retaining apparatus which may utilize the clip of FIG. 7;

FIG. 9 illustrate further retaining assemblies according to the present invention;

FIG. 10 illustrates yet another embodiment of the invention;

FIGS. 11 & 12 are opposed views of the mower blade illustrated in FIG. 10;

FIGS. 13 & 14 illustrate further forms of mower blades according to the invention, and FIG. 15 illustrates one form of cutter bar assembly according to the invention. The mower blade 10 shown in FIGS. 1 to 5 is adapted to be fitted to the baseplate 8 of a mower 9 and is formed from high-impact-strength plastics material. It includes a mounting portion 11 formed with a rounded inner end 12 provided with a mounting aperture 13. The front edge of the base portion 11 is shaped to form a cutting edge 14, and an inclined throwing flight 15 is joined to the base portion 11 along the edge opposite the front edge 14. The leading portion 17 of the blade 10 is thickened and tapers to a substantially constant cross-section along the V-section 18. The blade 10 is provided with ribs 16 which stiffen the blade and assist in their ability to discharge cut grass to a catcher or the like. The cutting edge 14 of the blade 10 angles forwardl-y and outwardly from the mounting part 11 so that the tip 23 leads the mounting part 11. The ribs 16 include longitudinal ribs 25 and transverse ribs 26 arranged substantially parallel and transverse respectively to the edge 27.

As illustrated, the mounting portion 11 is also thickened and tapers downwardly and inwardly to the rim 31 of a tapered annular recess 32 adapted to accommodate the tapered head flange 33 of a retaining assembly 35 as illustrated in Fig. 6. It is considered that the longitudinal ribs 25, which angle forwardly and outwardly, will provide a degree of mechanical engagement with the cut grass and assist in imparting a radial velocity thereto as the cut grass moves across the blades.

The retaining assembly 35 illustrated in FIG. 6 has a retaining pin 37 provided with a necked locking portion 38 and an intermediate support shank 39. The latter is stepped inwardly from the lower boss part 40 and is provided with a coarse thread section 41 which is engageable with a mating thread 42 formed in the bore 43 of a retainer 44.

In this embodiment, the lower face 45 of the retainer 44 is tapered so as to fit within a corresponding recess extending about the mounting aperture in the base plate 8. A . When clipped into position, the clip 46 prevents unscrewing of the retainer 44 and thus secure retention of the blade to the base-plate 8. The clip 46 is formed with a series of interconnected open ended apertures including a holding aperture 47 which fits firmly about the necked portion and an outer aperture 49 which is of a similar diameter but is more flexible due to its location at the outer ends of the arms 50. A small inner aperture 51 provides flexibility to the aperture 47. The outer aperture 49 enables simple initial connection to be effected for subsequent forcing of the clip 46 to its fully secured position.

The upper face of the retainer 44 is formed with an annular groove 52 in which a nib, shown dotted at 53 on the underside of the clip 46 engages when the aperture 47 is engaged about the pin 37.

To fit a blade 10 to a blade carrier 8, the old blade retaining bolt is removed from the blade bolt hole and discarded. The blade 10 is placed with the mounting aperture 13 adjacent to and in axial alignment with the blade bolt hole and the retaining pin 37 is forced through the bolt hole 13. The retainer 35 is then placed about the pin 35 and rotated until it is forced don onto the carrier 8. The clip 46 is then slid into position about the necked portion 38 and forced into position by thumb pressure. Removal is the reverse procedure.

The clip 55 illustrated in FIG. 7 is similar to the clip 46. However it is in the form of a disc 56 formed with opposing ridges 57 to enable it to be finger pushed in opposite directions. The interconnected apertures 58 include a mounting aperture 59 which may be inserted over the head 60 of the pin 61 of the retaining apparatus 62 illustrated in FIG 8. A holding aperture 63 interconnects with the aperture 59 through a waisted section 64 formed with cutouts 65 at opposite sides thereof to form resilient bridges 66 which may deflect to enable the necked portion 67 of the pin 61 to pass between the apertures 59 and 63. In this embodiment the pin shank 68 has a flat section 69 so that it may be retained non-rotatably in a correspondingly shaped carrier aperture. The clip 55 also has a nib 70 for engagement with a further aperture in the carrier disposed adjacent the aperture for the pin 61. The arrangement is such that when the pin is installed it will rotate until the nib 70 drops into the aperture provided therefor.

FIG. 8 illustrates another form of retaining apparatus 75 which is similar to the apparatus illustrated in FIG 6 but having a threaded shank 76 and a finger nut retainer 77. The clip 78 is provided with an apertured side extension which facilitates engagement by a screwdriver to lever the clip 78 from the pin 79. Respective side stops are also provided on the retainer and nut.

The embodiment illustrated in FIG 10 includes a retaining pin 80 formed of high-impact-strength plastics material and having a cylindrical body portion 81 adapted for engagement with the mounting aperture 82 of a base plate carrier 83. - A further cylindrical body portion 84 is adapted for engagement with a blade bolt aperture 85. The upper end of the retaining pin 80 is split and carries tapered lugs 86 which are adapted to engage over a conventional washer 87 after being forced through the washer so as to retain the plain blade 88, such as illustrated in FIG. 11, to the base plate 83.

The blade 90 illustrated in FIGS. 11 and 12 are form to a substantially constant thickness throughout and have plain upper and lower faces. However the upper face could be formed with a series of projections in the form of grass or air flow interference means if desired. The blades 91 and 92 illustrated in FIGS 13 and 14 are specifically adapted as grass throwing blades. They include a vane-like fence 93 an surface projections in the form of ribs 94 which curve in conformity with the fence 93 away from the cutting edge 95, or upstanding notches 96. . central bar 101 including a centralising aperture 102 and attachment apertures 103 for securing it to the shaft of a rotary mower. The outer ends 105 of the central bar 101 are formed with blade apertures 106 to which blades 107 may be attached with retaining pins 110. The retaining pins 110 are secured by placing over them tensioning washers 111 and locking collars 112 which include segmented recesses 113 which snap over flanges 114 and which are in turn retained by snap clips 115 having shaped recesses 116 which engage with recesses 117. OF course the retaining pins illustrated in FIG. 8 could be used if desired.

The central bar may be a plain steel bar or it may be formed from a plastics material and have a peripheral flange 120 which reinforces it and which forms semi-circular recesses 121 which partly enclose the snap-on clips 115 which engage the pins 110. The central bar 101, the blades 107, the retaining pins 110, the locking collars 112 and the snap clips 115 are all formed from a high-impact plastics material such as POLYCARBONATE for ease of forming by injection moulding or the like.

A safety aspect of this invention devolves from the use of a plastics material of much lower density than steel, combined with selective control over blade thickness such that the blade is as light as possible. This feature, along with the much greater deflection of the plastics material blade under load, results in a blade with a much greater tendency for inertial and elastic deflection under load, minimising injury in the event of impact with an article such as a loose stone or the foot of a user.

It will of course be realised that while the above has been given by way of illustrative example of this invention, all such and other 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 defined in the appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS;-

1. A cutting blade for a lawn mower or the like, the cutting blade being formed from a resilient plastics material and including:- a mounting portion having attachment means for connection to a blade carrier; a cutt-teg portion having a cutting edge formed along one elongate edge thereof; and flo interference means on the upper surface of the cutting portion.

2. A cutting blade as claimed in claim 1, wherein said attachment means includes a mounting aperture formed through said mounting portion.

3. A cutting blade as claimed in claim 2, wherein said mounting portion is formed with a recess extending about said mounting aperture.

4. A cutting blade as claimed in any one of the preceding claims, wherein said cutting portion is thickened adjacent said cutting edge.

5. A cutting blade as claimed in claim 4, wherein said thickened portion has a transverse extent which increases away from said mounting portion.

6. A cutting blade as claimed in any one of the preceding claims, wherein said flow interference means includes a plurality of ribs on the upper surface of said cutting portion.

7. A cutting blade as claimed in any one of the preceding claims, wherein said ribs include ribs which extend

8. A cutting blade as claimed in any one of the preceding claims and including air flow control means along the trailing edge of the cutting portion.

9. A cutting blade as claimed in claim 8 wherein said air flow control means includes an upturned throwing flight which extends along the trailing edge of the cutting portion.

10. Retaining apparatus suitable for attaching an apertured member to an apertured carrier, the retaining apparatus including:- a base portion adapted for retention by the apertured member; a retaining pin adapted for passage through the apertured member and the apertured carrier so as to locate one relative to the other, said pin having a necked portion which may be exposed at the side of the carrier remote from the apertured member, and a retaining clip engageable with said necked portion.

11. Retaining apparatus as claimed in claim 10, wherein said retaining pin and/or said retaining clip are formed from a plastics material.

12. Retaining apparatus as claimed in claim 10 or claim 11, wherein said pin includes a locking shank adjacent said necked portion and a retainer co-operable with said locking shank to prevent retraction of said pin through the apertured carrier.

13. Retaining apparatus as claimed in claim 12, wherein said retainer is a spacer which may de displaced axially along said locking shank to clip onto said locking shank.

14. Retaining apparatus as claimed in claim 12 or claim 13, wherein said retainer and said clip lock together.

15. Retaining apparatus as claimed in claim 12, wherein said retainer and said clip lock together through a recess formed in the upper face of the spacer and said holder accommodating a lug formed on said retaining clip.

16. A cutting blade assembly including a cutting blade as claimed in any one of claims 1 to 9 and retaining apparatus for retaining said cutting blade on a carrier, said retaining apparatus being as defined in any one of claims 10 to 15.

17. A cutting bar assembly including a cutter bar having a central connection for connecting the cutter bar to a drive shaft and retaining apparatus at each end thereof pivotally connecting cutting blades to each end of said bar.

18. A cutting bar assembly as claimed in claim 17, wherein said cutting blade is as claimed in any one of claims 1 to 9.

19. A cutting bar assembly as claimed in claim 17 or claim 18, wherein said retaining apparatus is as defined in any one of claims 10 to 15.

20. Mower cutting blade assemblies substantially as hereinbefore described with reference to the accompanying drawings.