GB2088685A

GB2088685A - Blade

Info

Publication number: GB2088685A
Application number: GB8136118A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-12-02
Filing date: 1981-11-30
Publication date: 1982-06-16

Abstract

A blade for lawn mowers and the like comprises a relatively flat body of hardened or toughened rubber-like material selected from vulcanized rubber and or synthetic rubber or resilient material selected from synthetic plastics or resins. The rubber-like material of the body may be reinforced with a layer or layers of woven or unwoven fibrous or fabric material. The body may include a metal insert (11). The ends of the blade may be provided with twisted portions (19, 20) to serve as updraught means. <IMAGE>

Description

SPECIFICATION A safety vegetation cutting blade for powered cutting devices This invention relates to cutting blades for vegetation cutting device such as lawn mowers, hedge trimmers and the like and particularly devices of various types having respectively, a horizontally rotating disc and two steel swivel blades or a single steel blade mounted on a vertical shaft and beneath a housing and is particularly concerned with the provision of a safety blade for both petrol engine and electric lawn mowers.

It is an object of this invention to provide a safety cutting blade for vegetation cutting devices.

The invention according to a general aspect resides in a safety cutting blade for petrol engine and electric vegetation cutting devices such as rotary lawn mowers, edgers, hedge trimmers and the like and comprises a relatively flat body of hardened or toughened rubber-like material selected from natural and/or synthetic rubber or resilient material selected from synthetic plastics or resins.

Preferably, the rubber-like material is reinforced with one or more layers of woven or unwoven fibrous or fabric material.

In one form of the invention preferred for use with petrol engine rotary mowers, the single safety cutting blade has completely embedded therein at least one flat metal mounting and/or rubber supporting strip insert which extends along a major supporting part of the blade.

More particularly and preferably, there is a single metal insert and both the metal insert and the blade are provided with a central bolt or shaft receiving aperture and more preferably with an aperture which is centrally located midway between the ends of the blade.

Preferably, the rubber-like material of the blade is reinforced with alternating layers of a plurality of nylon or polyester webbing strips and if desired, rubber bonding material layers being fabricated or integrally moulded in.

According to a further salient feature of the above described form of the invention, the safety blade of the present invention has end portions which extend beyond the embedded metal strip.

Preferably, the safety blade of the petrol motor mower form of the present invention is formed by moulding the embedded metal strip and alternating layers of nylon or polyester webbing as an integral unit.

Preferably, in all forms of the invention, the ends of the blade are provided with angled portions to serve as updraught means.

The rigid metal insert plate of the petrol motor mower is formed of a suitable steel, such as mild steel plate.

In one form of the invention, suitable for electric mowers, the blade has a flat dentre area and the side edges of each end are provided with four bevelled cutting edges in alternative pairs reversed on both ends of the blade to enable the blade to be laterally inverted, the end portion of each is laterally twisted about the longitudinal axis of each twisted end is off-set with respect to the other, to provide uplift draught portions.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a vegetation cutting blade constructed in accordance with the present invention suitable for petrol motor mowers.

Figure 2 is an end or profile view of the blade of Fig. 1.

Figure 3 is a plan view of a flat version of the vegetation cutting safety blade constructed in accordance with the present invention.

Figure 4 is a plan view of a flat version vegetation cutting safety blade constructed in accordance with the present invention.

Figure 5 is a side elevation of the blade of Fig. 4.

Figure 6 is an end profile view of the embodiment of Figs. 4 and 5.

Figure 7 is a partial cross section through the blades of Figs. 4 and 5.

Figure 8 is a plan view of a winged version of a vegetation-cutting safety blade constructed in accordance with the present invention.

Figure 9 is a side elevation of the blade of Fig. 8.

Referring to Fig. 1 of the drawings, there is shown a safety blade 10 of rubber reinforced with alternative layers of nylon or polyester webbing and having an integrally-moulded steel insert 11 embedded within the blade as shown in broken outline. The rigid steel insert extends along the flattened rectangular middle portion 1 2 of the blade and has a central aperture 1 3 in alignment with a central aperture 14 in the blade. The ends of the metal insert are both angled in the same direction below the general plane of the blade into the cutting edge section. The two end portions 1 5 and 1 6 of the blade extend beyond the metal insert and are more flexible then the middle portion.Each end portion has a bevelled or tapered cutting edge 1 7 and 1 8 disposed diametrically opposite sides with respect to each other and longitudinal axis of the blade.

The side of each end portion opposite to the cutting edge is curved into a wing configuration 19, 20 to cause an up-lift draught to propel grass cuttings into a catcher. Each end portion of the blade is arcuately shaped and angled about the longitudinal axis of the blade in an arcuate path which extends from below the plane of the flat middle portion of the blade to above the plane in the wing draught uplift plane as shown in the profile view of Fig. 2 of the drawings.

According to a modification of the above described embodiment of the invention, the metal namely the steel plate, may be omitted from cutting or trimming blades for such devices as edgers of flat configuration.

Referring to Figs. 4 and 5 of the drawings there is shown a safety blade 110, suitable for use with an electric lawn mower and made of rubber-like material reinforced with layers of fibrous material for example, nylon or polyester webbing or weave bonded to the rubber with bonding compound, if desired and having an integrally moulded-in metal insert, such as mild steel insert 111 embedded or encapsulated within the blade, as shown in dotted outline. The metal insert has a central, rectangular portion 11 2 extending along the flattened rectangular middle portion 11 3 of the blade and has a central aperture 114 in alignment with a central aperture or mounting hole in the blade.The metal insert tapers into triangular portions 115, 11 6 with rounded ends 11 7 and 118. The two end portions 119 and 120 of the blade extend beyond the metal insert and are more flexible than the middle portion. The side edges of each end portion have bevelled or tapered cutting edges 121, 122, 123, 124 respectively, which are reversibly disposed with respect to each other and the longitudinal axis of the blade to enable the blade to be laterally inverted for alternative use of the blades.

The profile view of Fig. 6, shows how each end of the blade is twisted laterally, out of alignment with the general plane of the blade to provide uplift.

Referring to Figs. 7 and 8, each end of the blade is angled in the same direction from the plane of the central area of the blade to form wings 1 25 and 1 26 to cause an uplift draught to propel grass cuttings into a grass catcher, such as a rear mounted catcher. In this embodiment, a mild steel insert emends partly into the angled cutting ends of the blade.

According to a modification of the invention, suitable for lightweight electric mowers and devices, the rubber may be hardened carboxylated nitrile rubber and the metal plate is omitted entirely from the safety blades or chopping and trimming devices having a cen trawl disc of nylon web reinforced rubber with integral "swept back" blades radiating from the central disc with one edge on a radius from the centre point of the disc, the other edge being at an angle to, or inclined to the radius line from the centre of the disc with an outer edge following a circumferential path. In this type of disc there are six equidistantly spaced blades of equal height.In another variation, there are three blades of swept-back configuration wherein both leading or cutting and trailing edges are curved and are integrally moulded to a central, circular disc portion.

In another variation, the safety blade is constructed of rigid, synthetic plastics material such as nylon/plastics elastomer preferably reinforced with chopped fibreglass and this can be used for cutting brush attached to electric or petrol engine driven vegetation cutting devices. The blades of these latter types of cutters are of elongated and truncated triangular configuration with bevelled edges along the leading, trailing and outer edges of the blades, which are preferably two or three in number and are integrally moulded to a central disc portion which may also have reinforcement webs particularly about a central attachment hole.

In a further variation of a cutting blade suitable for use with an electric motor mower, the blade is of shortened rectangular configuration with an embedded reinforcing plate of steel within a laminate structure of rubber and alternating layers of nylon web. Each alternate edge of this blade adjacent the end portion is bevelled to form a cutting edge and the body of the blade is twisted about the longitudinal centre line to provide uplift draught for grass cuttings, if a grass catcher is used. A central mounting hole is provided both in the blade and the steel reinforcing insert for mounting on the shaft of a mower.

Another feature or advantage of the invention, is that small objects which are hit by a spinning blade are not thrown out with the same violent force and velocity as with normal blades, but tend to be picked up and dropped more gently and at a smaller distance, likelihood of shaft damage is at least greatly reduced and substantially eliminated.

Claims

1. A safety vegetation cutting blade for petrol engine and electric cutting devices such as rotary lawn mowers, edgers, hedge trim mers and the like which comprises a relatively flat body of hardened or toughened rubber like material selected from vulcanized rubber and or synthetic rubber or resilient material selected from synthetic plastics or resins.

2. A safety vegetation cutting blade according to claim 1 wherein the rubber-like material of the body is reinforced with a layer or layers of woven or unwoven fibrous or fabric material.

3. A safety vegetation cutting blade ac cording to claim 1 or 2 wherein a single cutting blade is used of rubber-like material and has completely embedded therein, at least one flat metal mounting and/or rubber supporting strip insert which extends along a major part of the blade.

4. A safety vegetation cutting blade ac cording to any preceding claim wherein there is a single metal insert and both the metal insert and the blade are provided with a central bolt or shaft-receiving aperture.

5. A safety vegetation cutting blade according to claim 4 wherein the aperture is centrally located midway between the ends of the blade.

6. A safety vegetation cutting blade according to any preceding claim wherein rubber-like material of the blade is reinforced with alternating layers of a plurality of nylon or polyester webbing strips.

7. A safety cutting blade according to any preceding claim wherein the blade is formed by moulding an embedded metal strip and alternating layers of nylon or polyester webbing as an integral unit.

8. A safety vegetation cutting blade according to any preceding claim wherein the ends of the blade are provided with angled or twisted portions to serve as updraught means.

9. A safety vegetation cutting blade according to any preceding claim wherein the metal insert is a tempered steel plate.

10. A safety vegetation cutting blade according to any preceding claim suitable for lightweight electric mowers and cutting devices, the rubber is hardened carboxylated nitrile rubber.

11. A safety vegetation cutting blade according to claim 10 wherein the rubber is reinforced with nylon or polyester webbing.

1 2. A safety vegetation cutting blade according to any preceding claim which is in the form of a flat, elongated, rectangular plate.

1 3. A safety vegetation cutting blade substantially as hereinbefore described with reference to Figs. 1 to 3 of the drawings.

1 4. A safety vegetation cutting blade substantially as hereinbefore described with reference to Figs. 4 and 5 of the drawings.

1 5. A safety vegetation cutting blade substantially as hereinbefore described with reference to Figs. 8 and 9 of the drawings.