NZ250605A - Rotating drum comminuter blade structure - Google Patents

Description

250 605 PATENTS FORM 5 Number 250605 PATENTS ACT 1953 Dated December 30, 1993 COMPLETE SPECIFICATION BLADE STRUCTURE FOR COMMINUTING APPARATUS I, MATTHEW D'ORNAN KEITH DEAN of Kelly Road, RD 2, Mercer, New Zealand, a New Zealand citizen, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement r!7FEB 1995 7 25060 FIELD OF THE INVENTION This invention relates to blade structures for use on drum type comminuting equipment such as for instance stump chippers, rotary hoes, rotary slashers, wood chippers, brush and rubbish shredders and the like.

BACKGROUND TO THE INVENTION Comminuting equipment is generally used to remove wooden material such as tree stumps that have been left in or on the ground and typically consist of a rotating drum which has a number of teeth projecting substantially radially from its external surface so that as the drum rotates, the teeth will contact the stump and will break up the stump into smaller pieces and fragments. The drum can be constructed to be part of a prime mover such as a tractor or be constructed on a framework which can be towed by the prime mover. Power for the rotation of the drum is obtained either by a dedicated internal combustion engine or by suitable gearing through to the engine of the prime mover.

Because stump wood is generally hard and because of high impact forces exerted on the teeth, the teeth of the drum are subject to wear and damage and require replacement from time to time. It is therefore an essential requirement that the teeth be held firmly on the rotating drum yet be able to be removed and replaced as required.

Also, because of the manner in which the equipment is used, the teeth will encounter earth and other debris and it is often necessary to remove a considerable amount of this comparatively soft material during the comminution operation. This requires the teeth to be formed in a manner that not only will they break up the wood of a stump, but also must be able to move the debris from the work site. Known drum type comminuting equipment is generally deficient in this aspect.

PRIOR ART One form of comminuting machine is that disclosed in New Zealand Patent Specification 167,411. In that specification the machine comprised a rotating drum on which a number of shoes are attached to the periphery with each shoe carrying a removal 250 605 cutting member. That specification is particularly concerned with a method of facilitating the removal of the cutting member and for this purpose each cutting member is suitably held within a shoe which is attached to the periphery of the drum. The shoe is so positioned on the drum that the cutting member will project essentially radially from the periphery of the drum. A number of shoes are attached to the drum in a particular pattern so that each part of the material which passes over the drum will be subjected to a cutting action from one or more of the cutting members. A major disadvantage with the comminuting machine disclosed in the Patent Specification 167,411 is that because of the method of holding the teeth in each shoe, after a period of time and as a result of wear and oxidation, the teeth become very difficult to remove.

Another disadvantage with known forms of comminuting apparatus is that in use, the teeth of the drum can unexpectedly drag the drum against the stump, causing the depth of cut to become too great for the power of the motor and stall conditions can be encountered. Also with the type of machine disclosed in New Zealand Patent Specification 167,411 it is possible for a build-up of material and debris to absorb a considerable portion of the available motive power and restrict the cutting action of the teeth. A yet further disadvantage with the machine disclosed in New Zealand Patent Specification is that the shoes include shoulders outboard of the teeth and these shoulders wear, cause friction and absorb power.

OBJECT OF THE INVENTION It is therefore an object of this invention to provide an improved comminuting blade structure which will obviate or at least minimise the disadvantages of the known forms of such equipment.

SUMMARY OF THE INVENTION In broad terms, one form of the invention may be said to comprise a blade structure for a comminuting machine of the type having a rotatable drum with a peripheral surface and at least one blade structure mounted on the peripheral surface of the drum, wherein said blade structure comprises: • 3 - 250 60 5 at least three blade support ribs with each rib having an undersurface to conform to the shape of the periphery of the rotatable drum, an arcuate upper surface, a blade gap and a blade support surface, a backing plate attached to and extending between each blade support rib adjacent said blade supporting surface and having securing means to secure a blade to the backing plate and to locate the blade against the blade support surface, and a removable blade locatable in said blade gaps to extend across all of the said blade support ribs, wherein the said blade is attached to the backing plate by the securing means and has a portion which will project above the said arcuate upper surface of the blade support ribs.

Preferably the portion of the blade which extends above said arcuate upper surface is formed into a tooth.

Preferably the portion of the blade which projects above said arcuate upper surface is castellated to form a plurality of teeth.

Preferably the blade has a number of teeth which is equivalent to the number of blade support ribs.

Preferably the arcuate upper surface on the blade support rib provides a leading edge and a trailing edge respectively on either side of the said blade gap.

Preferably the leading edge of the blade support rib forms an arc which is less that ■\ £ u i- 7 2 5 0 8 0 the arc of the trailing edge of the support rib.

Preferably the leading edge of the blade support rib is of less height than the trailing edge.

Preferably, the blade support rib is formed of two parts, one part having the leading edge forming a base member which in use is spaced from the reminder of the blade support rib by the said blade gap.

Preferably the attachment means comprises a bolt which passes through a hole in the backing plate and engages in a screw threaded hole formed in said blade.

Preferably the part of the rib support member having the leading edge comprises a base member and wherein a fillet is located between and attached to contiguous base members.

In another aspect, the invention may be said to comprise a drum for a comminuting machine of the type having a rotatable drum with a peripheral surface and at least one blade structure mounted on the peripheral surface of the drum, wherein said blade structure comprises: at least three blade support ribs with each rib having an undersurface to conform to the shape of the periphery of the rotatable drum, an arcuate upper surface, a blade gap and a blade support surface, a backing plate attached to and extending between each blade support rib adjacent said blade supporting surface and having securing means to secure a blade to the backing plate and to locate the blade against the blade support surface, and a removable blade locatable in said blade gaps to extend across all of the said blade support ribs, wherein the said blade is attached to the backing plate by the securing means 250 605 and has a portion which will project above the said arcuate upper surface of the blade support ribs.

BRIEF DESCRIPTION OF THE DRAWINGS One form of the invention will now be described with the aid of the accompanying drawings wherein: Fig. 1 is a view of a blade structure according to the present invention in place on a drum of a stump chipper; Fig. 2 is an end view to a reduced scale of the blade structure shown in Fig. 1; Fig. 3 is a side view partly in phantom of the blade structure shown in Fig. 2; Fig. 4 is a view similar to that of Fig. 3 but showing the parts in a disassembled BEST MODE OF CARRYING OUT THE INVENTION Referring to the drawings and in particular Fig. 1, the blade structure of the present invention is intended to be utilised with the usual form of stump chipper drum, a portion of which is indicated diagrammatically at 1. Typically the drum 1 may be of one metre in width for example, with the width of the drum depending upon the mechanical power available and the maximum size of stumps the chipper is intended to handle, The drum 1 will be of a diameter to suit the circumstances.

A number of blade structures, one of which is indicated in Fig. 1, are located on the periphery of the drum. Each blade structure includes at least three blade support ribs 3 with each rib being attached to the peripheral surface of the drum 1 such as by welding or by other suitable method as known in the art and for this purpose the ribs 3 have an undersurface which will conform with the periphery of the drum to which the blade structure is to be attached. Each rib 3 has a blade support surface 3a and an arcuate external edge 3b, the radius of which diminishes so that the height of the arcuate surface is greater nearest the blade support surface 3a. The blade support ribs 3 should be of sufficient length and width to withstand the forces imparted to the blade structure during condition. 0 60 S use.

The blade structure also includes a base member which is located on the peripheral surface of the drum to provide a blade gap 4 between the blade support surface 3a of the ribs 3 and the base member. In one form, the base member may consist of ribs 10 each of which have an arcuate exposed edge 10a which has a radial height which is greater adjacent the gap 4. When the base member is in the form of a rib or ribs, the overall radial height of the arcuate external edge 3b of the blade support ribs 3 is preferably greater than the overall radial height of arcuate edge 10a of the ribs forming the base member, but this can be varied to suit particular circumstances. The length and depth of the ribs 10 is determined by considerations such as the desirability of smooth feeding of the material into the blade and to minimise the likelihood of debris wedging between the ribs. While for ease of manufacture, the front ribs will generally be of the same dimensions, the dimensions of some or all of the front ribs 10 can be varied to suit particular circumstances.

The blade gap 4 is of a dimension that it can receive a blade such as that indicated at 5 in the drawings. The blade has an outer edge preferably of a castellated formation to provide a number of teeth 6. Preferably but not necessarily the number of teeth is equivalent to the number of ribs 3. The leading edge 6a of each tooth is sharpened such as by being formed with a chisel edge as indicated in the drawings. The root 7 between each tooth 6 is also preferably formed as a chisel edge 7a similar to that of the edge 6a of the tooth 6.

The blade 5 is constructed so it may be removably attached to the blade structure after it has been inserted in the blade gap 4. One preferred means consists in forming a backing plate 8 which is attached to and extends between each contiguous rib 3 so as to lie adjacent the blade support surface 3a. Each backing plate 8 is suitably attached to the ribs, for instance by welding, and the height of the backing plate 8 will be less than the radial height of the edge 7a of the root between the teeth 6. The blade 5 is mounted on the blade structure preferably by forming screw threaded mounting holes in the blade 5 nV\- ~\\ 2 5 i"' 6 0 5 which will align with the corresponding mounting hole 8a in each backing plate 8. A bolt such as that indicated at 9 is passed through the mounting hole in each backing plate 8 and screwed into the appropriate screw threaded hole mounting hole 5a in the blade 5 so that the blade is secured to the blade support surface 3a of the blade support ribs by at least two bolts 9. It will be understood that each blade will have at least two screw threaded mounting holes to align with the respective mounting hole formed in each backing plate, thereby enabling the blade to be secured to the blade support ribs by at least two bolts.

As can be seen particularly in Figs 3 and 4, a fillet 13 is fixed to extend between the walls of contiguous ribs 10 with the leading edge 13a of the fillet 13 blending with the surface of the drum 1. The fillet 13 is of a size that it will partially fill the space between contiguous ribs as indicated in the drawings in order to minimise the likelihood of material wedging in front of the blade during use.

The particular shape chosen for the fillet 13 will depend upon the stall prevention and the soil trapping requirements. Similarly the relationship between the dimensions of the ribs and the fillet are somewhat interdependent since by reducing the size of the ribs 10 or increasing the size of the fillets 13, it is possible the size and shape of the ribs 10 and the fillets 13 can merge together, thereby eliminating the chamber between the ribs. In some circumstances such as when the teeth are to be subject to severe side loading, it can be advantageous for the fillet 13 to be fabricated as part of the blade.

In another form of the invention, although three ribs 10 are provided with the ribs preferably being equidistantly spaced apart from each other, the base member may comprise a lesser number of ribs 10, for instance the blade structure can include one rib 10 only and preferably this rib 10 will be located in substantial alignment with the middle rib 3 although the shape and positioning of the rib 10 in relation to the rib 3 can be varied as required.

In yet another form, the base member can comprise a member which extends transversely across the surface of the drum for a distance up to the width spanned by the :? r&& 8 ribs 3. Thus the base member can be of various shapes and sizes to suit the particular circumstances.

It will be understood the purpose of the base member is not only to provide support for the foot of the blade to prevent the base of the blade from kicking forward during use, but also to act as a means to minimise stall conditions through regulating the depth of cut by the teeth of the blade. In addition the area in front of the blade can be shaped that it will form an adequately sized collection area for loose soil and debris to assist in the dislodgement and discharge of debris and soil while minimizing the likelihood of large pieces of debris from becoming lodged in the collection area.

The drawings indicate one preferred method of removably attaching the blade to the blade structure by passing bolts 9 through appropriate mounting holes 8a in the backing plates 8, to engage screw threaded holes in the tooth 13. However other methods of arranging the attachment of the blade to the blade structure can be used as will be apparent to those skilled in the art.

In use, a number of blade structures are attached to the periphery of the drum 1 of the stump chipper so that as the drum rotates the teeth will all successively contact the stump to be chipped. For this purpose the blade structures can be offset in a longitudinal and radial direction on the periphery of the drum. The depth of the bite of the blade 5 will be limited by the size, shape and positioning of the base member 10. In addition when the base member is comprised of ribs, the space between contiguous ribs will allow comminuted material and debris to build up in the space below the arcuate edge of the ribs before it is expelled as a result of centrifugal force.

Although the blade structure as illustrated includes three ribs 3, a blade structure can be formed with any desired number of ribs 3. Preferably but not necessarily, the blade structure will have an equivalent number of ribs 3 and teeth 6.

While it is preferable the teeth as illustrated are essentially rectangular in shape and 2 5 0 6 0 5 are of substantially the same size, the teeth can be of differing shapes and sizes. In another form, some or all of the teeth can be twisted which in certain circumstances can provide an improved form of cutting action.

Because the teeth are braced in the manner shown by the ribs, the chances of the teeth breaking during use or bending or locking up on hard objects is minimised.

Preferably the blade structures are attached to the surface of the drum in a staggered relationship to each other, or in rows across the width of the drum. Depending on the particular placement of the blade structures and of the teeth, the rotating drum will provide an essentially flat finish or a grooved finish to the tree stump.

The specific advantage of the form of teeth as indicated in the drawings is that they can act efficiently as narrow teeth when cutting hard material whilst retaining the advantage of a large blade when moving soft material.

While the comminuting drum will normally be cylindrical in shape, the invention envisages the use of a drum of other shapes such as square, rectangular or other geometrical or non-geometrical shape in cross section. Such shaped drums are possible because the effective perimeter of the drum is the arcuate edges of the ribs 3 and therefore the perimeter of the drum will be essentially circular.

All existing technologies to maintain sharpness of the teeth can be utilized such as manufacturing the teeth from wear resistant alloy steels to the use of tungsten carbide inserts in the blade tips. Another option is to coat the wearing surface of the teeth with a hard wearing metal by welding techniques to maintain the desired sharpness.

The foregoing describes preferred forms of the invention. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated in the scope of the invention.

Claims (12)

250 60 5 WHAT I CLAIM IS:

1. A blade structure for a comminuting machine of the type having a rotatable drum with a peripheral surface and at least one blade structure mounted on the peripheral surface of the drum, wherein said blade structure comprises: at least three blade support ribs with each rib having an undersurface to conform to the shape of the periphery of the rotatable drum, an arcuate upper surface, a blade gap and a blade support surface , a backing plate attached to and extending between each blade support rib adjacent said blade supporting surface and having securing means to secure a blade to the backing plate and to locate the blade against the blade support surface, and a removable blade locatable in said blade gaps to extend across all of the said blade support ribs, wherein the said blade is attached to the backing plate by the securing means and has a portion which will project above the said arcuate upper surface of the blade support ribs.

2. The blade structure as claimed in claim 1, wherein the portion of the blade which extends above said arcuate upper surface is formed into a tooth.

3. The blade structure as claimed in claim 1, wherein the portion of the blade which projects above said arcuate upper surface is castellated to form a plurality of teeth.

4. The blade structure as claimed in claim 3, wherein the blade has a number of teeth which is equivalent to the number of blade support ribs.

5. The blade structure as claimed in any one of the preceding claims, wherein the arcuate upper surface on the blade support rib provides a leading edge and a trailing edge respectively on either side of the said blade gap. - 11 - v r D 25 0 60 5

6. The blade structure as claimed in claim 5, wherein the leading edge of the blade support rib forms an arc which is less that the arc of the trailing edge of the support rib.

7. The blade structure as claimed in claim 5 or in claim 6, wherein the leading edge of the blade support rib is of less height than the trailing edge.

8. The blade structure as claimed in any one of the preceding claims, wherein the blade support rib is formed of two parts, one part having the leading edge forming a base member which in use is spaced from the reminder of the blade support rib by the said blade gap.

9. The blade structure as claimed in any one of the preceding claims, wherein said attachment means comprises a bolt which passes through a hole in the backing plate and engages in a screw threaded hole formed in said blade.

10. The blade structure as claimed in claim 5, wherein the part of the rib support member having the leading edge comprises a base member and wherein a fillet is located between and attached to contiguous base members.

11. A blade structure for a drum of a comminuting machine substantially as herein described with reference to the accompanying drawings.

12. A drum for a comminuting machine including the blade structure as claimed in any one of the preceding claims. / ^EG WEST-WALKER & CO