GB2312365A - Device for cutting grass - Google Patents

Abstract

A device for cutting grass around low, ground level or buried objects comprises a rotary cutter which is positionable over such an object 10. The rotary cutter has cutter elements 24 adapted, when the cutter is positioned over such an object 10 and rotated at high speed, to perform a circular cutting of grass G around the object.

Description

DEVICE AND METHOD FOR GRASS CUTTING This invention relates to grass cutting, and is particularly concerned with the trimming of grass around objects which are set into the ground, and which cannot be cleared by normal mowing.

As used herein, the term "grass cutting" is intended to embrace the cutting of not only grass itself but more generally any low level vegetation which may be grown to provide a recreational, sports, or games playing surface, or a crop.

The task of trimming long grass growing at the base of objects projecting above ground level has in recent years been made easier by the use of a handheld garden power tool which has become known as a strimmer". Using such a tool it is possible to trim right up against the projecting objects, such as tree trunks, walls, fences, washing line poles, etc.

without the need to use hand-operated tools such as shears, clippers etc.

Fig. 1 of the accompanying drawings illustrates schematically the basic components of such a strimmer.

The device includes a stem 1 formed at its upper end with a handle 2, and carrying at its lower end a grass cutting assembly 3. This assembly includes a rotary cutter 4 mounted for rotation about an axis coincident with the lower end of the stem and an arcuate protective guard 5. This guard covers the rear part of the cutting circle formed by the rotating cutter so as to prevent rearward projection of stones etc., a forward part of this cutting circle being exposed to allow cutting at this point to take place. The cutter itself may comprise a length of nylon wire which is fed out from a central rotating spool or, in more heavy duty strimmers, a diametric blade bolted or otherwise fixed centrally to a rotary spindle. Rotary power may be provided by an electric motor contained in a housing formed at the lower end of the stem 1, but in heavy duty devices and/or where strimming is to be carried out at remote locations where electrical power is unavailable, a small petrol engine is provided.

When strimming around an object surrounded by the grass, such as a washing line pole, the user holds the strimmer with the exposed part of its rotating cutter immediate adjacent to the object so that the grass or other vegetation is cut to the required height.

One example of a situation where grass trimming is a practical necessity is in grass irrigation systems where a number of water sprinklers are set into the turf over a grassed area, e.g. in parks, large lawns and golf courses.

Fig. 2 of the accompanying drawings illustrates a typical sprinkler device 10 used in such irrigation systems. It comprises a generally conical housing 11 set into the turf, and a circular cap 12 mounted so as to close the top of the housing. A water sprinkler mechanism illustrated schematically at 13 and fed from a water main is contained within the housing 11, and is axially displaceable from the closed position shown in solid lines to the raised position shown in broken lines, automatically when the water supply is turned on from a remote location, to allow water W to be sprayed from the sprinkler device outwardly through the annular gap 14 formed beneath the rim of the cap 12 when the mechanism and the cap are raised.

Fig. 2a shows the grass G neatly trimmed at the edge 15 of the hole in which the device is accommodated, but it will be appreciated that if this surrounding grass is allowed to grow too long, as shown in Fig. 2b, it will interfere with the spraying action and deflect the water sprayed through the gap 14, thus impairing the spraying action by reducing the spraying range and disturbing the evenness of the spray. If allowed to grow very long, this grass may even prevent the cap from raising properly when the water is turned on.

Trimming around these sprinkler heads is therefore a matter of high priority in maintaining the efficiency of the sprinkler system and in systems covering wide areas, such as golf courses, this task is extremely labour-intensive and time-consuming when using conventional trimming tools. It will be appreciated that a conventional strimmer, as described earlier with reference to Figure 1, is unsuitable for this task.

The present invention is aimed at alleviating these problems, and making the task of trimming around such low, ground level or buried objects as fixed sprinkler heads less difficult and time consuming. To that end, the invention provides in one aspect a device for cutting grass growing around low, ground level or buried objects, comprising a rotary cutter which is positionable over the object from above and which has cutting means adapted, when the cutter is so positioned and then rotated at high speed, to perform a circular cutting of the grass around the object.

The invention also provides a method for cutting grass growing around low, ground level or buried objects using a device as defined above, the method including positioning the rotary cutter over the object with said cutting means projecting downwardly outside the object, and rotating the cutter at high speed so as to cause the cutting means to perform a circular cutting around said object.

The device is preferably in a form suitably adapted to be fitted to the drive spindle of a strimmer in place of its usual cutter.

The invention includes a rotary cutting device for cutting grass growing around low, ground level or buried objects, the device being adapted to be positionable over such an object and having at least one cutter element adapted to perform a circular cutting about such an object when rotated and vanes rotatable with the or each said cutter element for chopping the cut grass and dispersing chopped grass radially outwardly of the device.

In order that the invention may be well understood, some embodiments thereof, which are given by way of example only, will now be described with reference to the drawings, in which: Fig. 1 is a perspective view illustrating schematically the essential components of a grass strimmer; Figs. 2a and 2b illustrate the construction of a typical sprinkler head in a sprinkler system, Fig. 2a showing the device with its surrounding grass properly trimmed, and Fig. 2b showing it with the grass overgrown; Fig. 3 shows a first embodiment of a cutting device according to the present invention, as seen from the underside thereof; Fig. 4 is a sectional view of the cutting device shown in Fig. 3, taken on the line IV-IV; Fig. 5 is a top plan view of the cutting device shown in Figs. 3 and 4; Figs. 6a and 6b are fragmentary views showing respectively the shapes of two kinds of vane included in the cutting device of Figs. 3 to 5; Fig. 7 illustrates a strimmer fitted with the cutting device of Figures 3 to 6, as used for trimming the hole in which a sprinkler device of Figure 2 is set; Fig. 8 is a top plan view of a second embodiment of a cutting device according to the invention; Fig. 9 is a sectional view on line IX-IX in Figure 8; Fig. 10 illustrates a strimmer fitted with the cutting device of Figures 8 and 9, as used for trimming the hole in which a sprinkler device of Figure 2 is set; Fig. 11 is a view corresponding to Figure 8 showing a modified version of the second embodiment of a cutting device according to the invention; and Fig. 12 is a section on line XII-XII in Figure 11.

The idea underlying the present invention is based on the realisation that for low, ground level or buried objects such as the afore-mentioned sprinkler heads, it is possible to strim from above and rapidly perform a circular cut around the object. The cutting devices illustrated in Figs. 3 to 7 and 8 to 10 of the accompanying drawings are designed so as to facilitate this method of strimming from above.

A first embodiment of the cutting device is shown in Figures 3 to 7 and comprises cutting means comprising a support element which is generally in the shape of a disc 20 and is adapted to be fitted to the rotary spindle of a strimmer in place of the normal diametric cutter blade. For this purpose, the disc 20 is provided with a central circular aperture 22; the method of fixing the disc will be described later.

The cutting means further comprises a plurality (in this case four) of circumferentially spaced cutter elements 24 which project downwardly from the peripheral part of the underside of the disc, namely the side which will face downwardly in use.

The underside of the disc is also provided with a plurality (in this case twenty-four) of circumferentially spaced vanes 26 projecting from the disc surface. Each vane has a radially inner part 28 extending obliquely to a disc radius Rv passing through the radially inner end 27 of the vane and a radially outer part 30 which curves back toward that radius, and which terminates at the disc periphery.

A plurality of these vanes (four in this case) 26' are formed also with respective cutter elements 24. As best seen in Figs. 4 and 6b of the drawings, each said cutter element 24 adjoins the outer part 30 of a respective one of the four particular vanes 26', and is slightly curved in section, in the opposite sense to the curvature of the outermost part 30 of the vane.

The lower face 35 of the disc from which the cutter elements 24 and the vanes 26 project is slightly conical so that the thickness of the disc reduces radially outwardly from the disc center, as best seen in Fig. 4. The lower edges 27 of the vanes 26, 26' lie in a plane perpendicular to the disc axis, and the height of the vanes from the disc face 35 increases radially outwardly, again as best seen in Fig. 4. The upper face 36 of the disc is flat.

The cutter device of the present embodiment may conveniently be produced as a one-piece integral component by injection moulding from a suitable thermoplastics material, such as nylon, polyethylene or PVC.

To secure the device to the spindle of a strimmer, a suitably adapted bolt 40, illustrated in broken line in Fig. 4, is passed through a washer 41 and the central aperture 22, and is screwed into a central threaded bore 44 of the spindle 42. The bolt may be formed with a hexagonal head portion 46 to facilitate tightening using a spanner. The spindle includes a flange 43 against which the device is clamped when the bolt is tightened.

The bolt head is preferably also formed with a central conical projection 48, to assist proper positioning of the cutting device, in use, over a sprinkler head.

Thus, in use of the device when fitted as described above, the strimmer 1' is placed so that the cutter disc 20 lies directly over the sprinkler 10, the cap portion 12 of which is normally formed with a central recess 12a (accommodating the head of a screw which fixes the cap 12 to the mechanism 13) and shown in Figure 7. The user then adjusts the position of the strimmer until it is felt that the conical head portion 48 of the fixing bolt 40 is properly located in the cap recess 12a. In this position of the cutter disc, the cutter elements 24 will each project downwardly outside the cylindrical side wall of the cap 12 inside the edge of the hole 15, and it will be appreciated at this point that the spacing of the cutter elements 24 from the disc center is adapted according to the outer diameter of the particular sprinkler head 10 in the irrigation system.

Once the cutter head has been correctly positioned in this way, the strimmer is actuated and the disc 20 rotated. The cutter elements 24 thus trim the grass G growing inwardly from the edge 15 over the cap 12 thereby ensuring that when the sprinkler device is actuated and the cap/sprinkler mechanism raised the annular sprinkling gap 14 will be left unobstructed by the grass.

The standard direction of rotation in strimmers is anticlockwise (viewed from underneath), so that the cutter device illustrated in the drawings will rotate as shown by arrow A in Fig. 3. The vanes 26, 26' act as an impeller creating a radially inward draught which tends to draw the blades of grass radially of the hole for maximum cutting efficiency. The rotating vanes chop the cut grass and create a pressure beneath the disc which disperses the chopped grass away from the head, leaving the edge 15 clean and neatly trimmed.

A second embodiment of the cutting device is shown in Figures 8 to 10. The cutting device of the second embodiment is generally similar to the first embodiment. Accordingly, like reference numerals will be used to describe corresponding or similar features.

The cutting device of the second embodiment comprises cutting means comprising a support element in the form of a disc 20 and a plurality (in this case four) of circumferentially spaced first cutter elements 24 which project downwardly from the peripheral part of the underside of the disc in a direction substantially parallel to the axis of rotation of the disc.

The underside of the disc 20 is provided with a plurality (in this case twenty-four) of circumferentially spaced vanes 26 projecting from the disc surface.

The lower face 35 of the disc from which the first cutter elements 24 and the vanes 26 project is slightly conical so that the thickness of the disc reduces radially outwardly from the disc center.

The second embodiment of the cutting device differs from the first embodiment by the provision of a plurality (in this case four) of second cutter elements 50 which are adapted so as to project, in use, transversely of the disc 20.

The second cutter elements are in the form of flat elements or blades 50 provided with a throughhole at one end thereof. The upper face 36 of the disc is provided with four integrally formed projections 52; one projection for each blade 50. The projections 52 have a circumferentially extending groove and the through-holes of the blades are adapted such that the blades can be mounted to their respective projections by snap-fitting engagement of the through-holes and grooves.

When mounted to their projections 52 the blades 50 are freely rotatable thereon such that, in use, the blades will extend outwardly of the periphery of the disc 20 to the positions shown in Figure 8 under the influence of centrifugal force.

Referring to Figure 10, the cutting device of the second embodiment is used in the same way as the first embodiment as described above. In particular the first cutter elements 24 cut through a circular path trimming the grass growing inwardly from the edge 15 over the cap 12 of the sprinkling device 10.

The blades 50 are caused to extend outwardly of the outer periphery of the disc 20 as it rotates at high speed during the cutting process and cut through a second circular path having a radial extent which is greater than the radial extent of the first circular path. The blades 50 cut through the grass G surrounding the edge 15 of the hole for the sprinkler device. It will be appreciated that the extent of the annular cutting path described by the second cutter elements will depend on the extent of the projection of the blades 50 beyond the outer periphery of the disc 20.

It will be understood that the cutting device of the second embodiment provides the advantage that the grass surrounding the sprinkler hole can be trimmed simultaneously with the grass growing inwardly of the edge 15 hole to an extent which allows the remainder of the grass in the region of the sprinkler hole to be cut with a conventional lawn mower in such a way that during the mowing operation the operative can easily steer clear of the vicinity of the sprinkler device.

The second cutter elements are preferably freely rotatable blades 50 as described above. If desired the blades 50 may be biassed by, for example, springs to a position in which they do not project beyond the outer periphery of the disc 20.

In a less advantageous embodiment the second cutter elements may be fixed in their projecting position. However, it will be appreciated that such a configuration will be more susceptible to damage than is the case when the blades are rotatably mounted to the disc.

Advantageously, the disc 20, first cutter elements 24 and projections 52 are produced as a onepiece integral component by injection moulding utilising a suitable thermoplastics material as described above. Of course if the blades 50 are fixed these may be formed integrally with the disc.

The rotatably mounted blades 50 are preferably mounted to the disc 20 by a snap-fitting arrangement.

However other forms of rotatable fixing will be readily envisaged by the skilled person.

It will be appreciated that the described cutting devices can be modified in many ways without departing from the scope of the invention as defined in the attached claims. For example, the number and form of the cutting elements can be varied, as can the means of attachment to the rotary strimmer spindle. Also, while the described device is intended for cutting around a buried object, in this case a sprinkler head, it could also be used on objects which have a limited projection above ground level.

Figures 11 and 12 show a modification of the second embodiment of the cutting device and accordingly like reference numerals will be used to describe corresponding or similar features.

The modified cutting device is provided with recesses 70 in the upper side of the support disc 20.

These recesses 70 define radially extending ribs 72.

In all other respects the modified cutting device corresponds to the second embodiment.

The provision of the recesses 70 in the support disc provides two advantages: firstly the amount of material in the disc is reduced thereby reducing material costs and reducing the rotating mass of the device; and secondly if the disc 20 and first cutting elements 24 are made as an integral plastics moulding, the recesses facilitate removal of the disc from the moulding tool at the end of the moulding cycle.

Claims (22)

CLAIMS:

1. A device for cutting grass growing around low, ground level or buried objects, comprising a rotary cutter which is positionable over the object from above and which has cutting means adapted, when the cutter is so positioned and then rotated at high speed, to perform a circular cutting of the grass around said object.

2. A device according to claim 1, wherein said cutting means comprises a support element to be placed over said object and adapted to be rotated at high speed around a rotary axis, and a plurality of circumferentially spaced cutter elements, each provided at substantially the same radial spacing from said rotary axis, and projecting in a direction substantially parallel to the rotary axis from one side of said support element.

3. A device according to claim 1 or 2, further including means to create an airflow when the cutter is rotated at high speed, said airflow being directed radially inwardly so as to draw the grass into the path of said cutting means.

4. A device according to claim 3 when dependent on claim 2, wherein said means for creating an airflow comprises an array of circumferentially spaced vanes formed on said one side of said support element.

5. A device according to any preceding claim, wherein said rotary cutter is a one-piece, integrally formed component.

6. A device according to claim 5, wherein said component is formed from a thermoplastics material.

7. A device according to claim 1, wherein said cutting means is adapted to simultaneously perform a first and a second circular cutting of grass around said object, said second circular cutting having a greater radial extent than said first circular cutting.

8. A device according to claim 7, wherein said cutting means comprises a support element to be placed over said object and adapted to be rotated at high speed about a rotary axis, at least one first cutter element projecting from one side of said support element in a direction substantially parallel to said rotary axis for performing said first circular cutting and at least one second cutter element projecting, or adapted for projecting in use, outwardly of the outer periphery of the support element for performing said second circular cutting.

9. A device according to claim 8, wherein the or each said second cutter element is rotatably mounted to said support element such that, in use, the cutter element projects outwardly of the outer periphery of said support element under the influence of centrifugal force.

10. A device according to claim 11, wherein the or each said second cutter element is spring-biassed to a non-projecting position.

11. A device according to claim 9 or 10, wherein the or each said second cutter element is mounted to a respective projection provided on said support element, the or each said projection being adapted to be snap-fittingly engageable with a said second cutter element.

12. A device according to any one of claims 8 to 11, wherein the or each said second cutter element is mounted to the side of said support element opposite said one side.

13. A device according to any one of claims 8 to 12, further including means to create an airflow when the cutter is rotated at high speed, said airflow being directed radially inwardly so as to draw the grass into the path of said first cutter elements.

14. A device as claimed in claim 13, wherein said means for creating an airflow comprises an array of circumferentially spaced vanes formed on said one side of said support element.

15. A device according to any one of claims 8 to 14, wherein at least said support element and the or each said first cutter element is a one-piece integrally formed component.

16. A device according to any preceding claim, wherein said rotary cutter is adapted for attachment to a rotary drive member of a strimmer.

17. A device according to claim 16, wherein said rotary cutter is formed with a central aperture for accommodating a fixing bolt.

18. A rotary cutting device for cutting grass growing around low, ground level or buried objects, the device being adapted to be positionable over such an object and having at least one cutter element adapted to perform a circular cutting about such an object when rotated and vanes rotatable with the or each said cutter element for chopping the cut grass and dispersing chopped grass radially outwardly of the device.

19. A device according to claim 2 or any claim dependent thereon wherein said support element is formed with recesses on its side remote from the cutter elements, said recesses defining radially extending ribs.

20. A method for cutting grass growing around low, ground level or buried objects using a device according to any preceding claim, the method including positioning the rotary cutter over such an object and rotating the cutter at high speed so as to cause the cutting means to perform a circular cutting around said object.

21. A device for cutting grass growing around low, ground level or buried objects, substantially as hereinbefore described with reference to Figures 3 to 7 or 8 to 10 of the accompanying drawings.

22. A method for cutting grass growing around low, ground level or buried objects, according to claim 18 using a device according to claim 19.