GB2200271A - Cutter head for hedge cutter - Google Patents

Abstract

A cutter head 1 for a hedge cutter comprises a hollow shaft 2 having a plurality of V-shaped brackets 3 symmetrically arranged around the periphery of the shaft. A tubular bushing support 16 is carried in the apex of each bracket 3 and a nylon bushing 10 is removably mounted in the support 16 by a pivot bolt 5. A flail 4 is carried by each bracket 13. To prevent damage to the brackets 3, is use, annular discs 11 are provided at the ends of the shaft 2. <IMAGE>

Description

A CUTTER HEAD FOR A HEDGE CUTTER The present invention relates to a cutter head for a hedge cutter.

Conventional hedge cutters are normally mounted on a tractor or similar vehicle and driven from the hydraulic system of the vehicle.

One typical cutter head comprises a rotatable shaft having a number of brackets arranged around the periphery of the shaft and having a flail pivotally mounted on each bracket. Each bracket consists of a pair of spaced apart plates projecting radially from the shaft and having a through hole for reception of a flail pivot bolt. The flail is generally a substantially U-shaped metal plate having an inner portion and a pair of substantially parallel arms adjacent and between the free ends of which is mounted a bushing for reception of the flail pivot bolt.

These cutter heads are of fairly substantial construction and operate at relatively high speeds. Thus, it is necessary that they be dynamically balanced. In use, typically after about six weeks of constant use, the flails wear out and have to be replaced. The construction of flail and bracket is such that the flail pivot bolt causes ovality in the bracket through holes. Hence the cutter head becomes unbalanced even with replacement flails fitted. Eventually the wear is such that the cutter head has to be discarded.

A further disadvantage of this type of cutter head is that when in use the mounting brackets can be damaged if the rotating cutter head is allowed get too close to the ground or other immovable obstacles such as tree trunks or rocks.

There is therefore a need to provide an improved construction of cutter head which overcomes these problems.

The present invention is directed towards providing such a cutter head.

According to the invention there is provided a cutter head for a hedge cutter having a rotatable shaft with a plurality of radially projecting mounting brackets arranged around the periphery of the shaft and a flail mounted on each bracket by a pivot pin, wherein the contact area between the pivot pin and the bracket is substantially greater than the contact area between the pivot pin and the flail.

In a particularly preferred embodiment of the invention the. contact area between the pivot pin and the bracket is provided by a bushing.

Preferably, the bushing extends substantially the width of thG bracket.

In a preferred embodiment of the invention the bushing is removably mounted to the bracket.

In one embodiment of the invention the bushing is mounted in a bushing support provided on the bracket.

Preferably the bushing support comprises a tube for receiving the bushing.

Preferably the bushing comprises a tube of wear resistant material.

Typically a steel bushing is provided. In a further embodiment the bushing is of a plastics material.

In one embodiment of the invention the pivot pin is provided by a pivot bolt.

In one embodiment of the invention each mounting bracket is of substantially V-shape in radial cross-section, the bushing being rotiinod in the apex of the V.

Preferably, the mounting bracket is formed by a plate member bent intermediate the ends thereof into the V shape.

In a preferred embodiment of the invention the shaft is provided with a flange adjacent at least one end thereof, the flange projecting beyond the outer radial edge of the mounting brackets, in use.

Preferably a pair of flanges are provided, one adjacent each end of the shaft.

Typically, the or each flange is provided by an annular disc.

In one embodiment of the invention, each flail comprises a U-shape plate member comprising an outer blade member and a pair of inwardly extending arms, each of the arms having a hole for reception of the pivot pin.

The invention will be more clearly understood from the following description of an embodiment thereof given by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a perspective, partially exploded view of a cutter head according to the invent ion, Fig. 2 is a sectional view of the cutter head taken through the sectional lines II-II of Fig. 1, Fig. 3 illustrates a mounting bracket portion of a cutter head according to another embodiment of the invention, and Fig. 4 is a plan view of the mounting bracket of Fig. 3.

Referring to the drawings, and initially to Figs. 1 and 2 there is illustrated a cutter head for a hedge cutter, indicated generally by the reference numeral 1, The cutter head 1 comprises a. rotatable hollow shaft 2 having a plurality of radially projecting mounting brackets 3 symmetrically arranged around the periphery of the shaft 2. A U-shaped flail 4 is mounted on each mounting bracket 3 by a bolt 5 forming a pivot pin.

An annular disc 11 forms a flange at each end of the shaft 2. Each annular disc 11 has an outer radial edge 12. The outer diameter of each disc 11 is such that none of the mounting brackets 3 project beyond the outer radial edge 12.

Each mounting bracket 3 is of substantially V-shape having an apex 7 and a pair of diverging arms 8 each terminating in a free end 9 where it is secured to the shaft 2. Within the apex 7 of the mounting bracket 3 is welded a tube 16 which retains a bushing 10. The bushing 10 is a push fit in the tube 16 and is bored to receive the bolt 5. The bushing 10 is prevented from rotating within the tube 16 by means of a grub screw 18.

Each flail 4 is a substantially U-shaped metal plate comprising an inner portion 13 and a pair of substantially parallel outer arms 14. Each arm 14 has through holes 15 for reception of the bolt 5. Each flail 4 has bevelled cutting edges 17 along both sides of the inner portion 13 and outer arms 14.

The bolt 5 secures the flail 4 to the mounting bracket 3 passing through the arms 14 of the flail 4 and the bushing 10 and is secured in position by a nut 6.

In use, the cutter head 1 is mounted on a tractor or similar vehicle and driven from the hydraulic system of the vehicle. The hedge cutter is operated in conventional manner. It will be appreciated that when in use the major wear at each point where a flail 4 is attached to a mounting bracket 3 occurs at the through holes 15 of the flail 4 and the points of contact between the flail 4 and the bolt 5. This wear is acceptable and of no great consequence as these flails 4 typically have a useful working life of about six weeks when in constant use and them have to be replaced anyway. Should it be necessary to replace a bushing 10 the nut 6 is unscrewed from the bolt 5 and the bolt 5 is removed, allowing the bushing 10 to be readily removed from the tube 16 and replaced. Such replacement is required only after prolonged useful life.

An advantage of the present invention is that it minimises wear of the mounting brackets by the flail pivot bolt thus extending the useful working life of the cutter head. This is achieved by having a bushing support for the flail pivot bolt in each bracket. As the flail pivot bolt is supported over most of its length by the bushing there will be relatively little wear between the bushing and the pivot bolt. Should any excessive wear occur at a bushing, it can easily be replaced at minimum cost.

A further advantage of the invention is that the annular discs located at each end of the rotatable shaft provide protection for the cutter head. The annular discs help to prevent undue damage to the rotating cutter head assembly by keeping the rotating shaft and mounting brackets at a distance from the ground or other unyielding obstacles such as tree trunks or rocks.

Referring now to Figs. 3 and 4, there is illustrated a mounting bracket 20 portion of a cutter head according to another embodiment of the invention. Parts similar to those described with reference to the previous drawings are assigned the same reference numerals. In this case, the bracket 20 is of cast steel and again is of substantially V-shape having an apex 21 and a pair of diverging arms 22 each terminating in a free end 23. A through hole 24 is provided in the apex 21 for mounting of the bushing 10. A number of these brackets 20 are attached to the shaft 2 of a cutter head in similar fashion to the brackets 3 illustrated in Fig. 1.

It will be appreciated that any suitable construction of support bracket may be employed for mounting the bushing.

It will also be appreciated that the bushing may be of any suitable material of construction, for example, steel or a plastics material.

It will further be appreciated that any suitable construction of flail may be used.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail.

Claims (19)

1. A cutter head for a hedge cutter having a rotatable shaft with a plurality of radially projecting mounting brackets arranged around the periphery of the shaft and a flail mounted on each bracket by a pivot pin, wherein the contact area between the pivot pin and- the bracket is substantially greater than the contact area between the pivot pin and the flail.

2. A cutter head as claimed in claim 1 wherein the contact area between the pivot pin and the bracket is provided by a bushing.

3. A cutter head as claimed in claim 2 wherein the bushing extends substantially the width of the bracket.

4. A cutter head as claimed in claim 2 or 3 wherein the bushing is removably mounted to the bracket.

5. A cutter head as claimed in any of claims 2 to 4 wherein the bushing is mounted in a bushing support provided on the bracket.

6. A cutter head as claimed in claim 5 wherein the bushing support comprises 2 tube for receiving the bushing.

7. A cutter head as claimed in any of claims 2 to 6 wherein the bushing comprises a tube of wear resistant material.

8. A cutter head as claimed in claim 7 wherein the bushing is of a nylon material.

9. A cutter head as claimed in any preceding claim wherein the pivot pin is provided by a pivot bolt.

10. A cutter head as claimed in any of claims 2 to 9 wherein each mounting bracket is of substantially V-shape in radial cross-section, the bushing being retained in the apex of the V.

11. A cutter head as claimed in claim 10 wherein the mounting bracket is formed by a plate member bent intermediate the ends thereof into the V shape.

12. A cutter head as claimed in any preceding claim wherein the shaft is provided with a flange adjacent at least one end thereof, the flange projecting beyond the outer radial edge of the mounting brackets, in use.

13. A cutter head as claimed in claim 12 wherein a pair of flanges are provided, one adjacent each end of the shaft.

14, A cutter head as claimed in claim 12 or 13 wherein the or each flange is provided by an annular disc.

15. A cutter head as claimed in any preceding claim wherein each flail comprises a U-shape plate member comprising an outer blade member and a pair of inwardly extending arms, each of the arms having a hole for reception of the pivot pin.

16. A cutter head as claimed in any preceding claim wherein the bracket is cast from a castable material.

17. A cutter head as claimed in claim 16 wherein the bushing support is integrally cast with the bracket.

18. A cutter head substantially as hereinbefote described with reference to the accompanying drawings.

19. A hedge cutter incorporating a cutter head as claimed in any preceding claim.