CA3012635A1 - Self-maintaining vegetation blade - Google Patents

Abstract

A blade for use with vegetation is provided, the blade having a blade body with a blade end, an attachment end, a first face, and a second face. The first and second faces are separated by a thickness of the blade body, and the blade end has an end edge that is substantially parallel to an intended direction of travel of the blade body during use, and a blade edge that is adjacent to the end edge. The blade edge has a concave recess that intersects with the end edge to define a contact point, the contact point redirecting at least a portion of the vegetation into the concave recess such that the concave recess and the contact point are maintained as the blade end erodes. The concave recess has an engagement surface that is flat and extends perpendicularly between and relative to the first and second faces.

Description

SELF-MAINTAINING VEGETATION BLADE
TECHNICAL FIELD
[0001] This relates to a blade used to remove vegetation, such as may be found on a brush cutter or mower, and in particular, a blade that is self-maintaining.
BACKGROUND

[0002] There are many instances where various mowers and brush cutters are used in unimproved cutting conditions to control unwanted vegetation including grasses and brush regrowth. Traditionally cutting edges have been employed to sever the stems of the vegetation, such as represented by a knife, scythe or a powered lawn mower.

[0003] Road side ditches, utility rights-of-way, and agricultural lands are some locations where vegetation control requires engaging heavy vegetation, brush and trees in an unimproved context where gravel, rocks and other debris cause damage and excessive wear to surfaces that impact the vegetation. Some of these wear surfaces and their respective machines are heavy duty enough to be classified as disc type (vs. drum type) tree mulchers.

[0004] Most of these disk type mulching devices engage the vegetation with relatively flat "blade" shapes that employ a knife-edge to deliver a severing force to the vegetation.
These blades are typically mounted on a rotating blade holder and, for heavier vegetation in unimproved conditions, also incorporate some method to allow the blade(s) to pivot on the moving blade holder. This allows the blade to "swing away" as the blade contacts potentially damaging objects such as rocks etc.

[0005] Traditionally the blade's knife-edge that delivers the force to the vegetation is sharpened after a conventional "knife pattern" where the length of the leading edge has one or more bevels on it so as to present a knife-like edge to the surface it is intended to sever. As the blade is used, the knife edge dulls and is either re-sharpened by some method or the blade is discarded and replaced.

[0006] Another type of cutter is a rotary, or drum style cutter, where cutter elements are mounted to the drum, which rotates and cuts through vegetation as the rotary cutter elements come into contact with the vegetation.
SUMMARY

[0007] According to an aspect, there is provided is a vegetation engaging member that presents a suitably small point of contact, which when impacting the vegetation, concentrates and amplifies the abrading force which severs the stem. In some aspects, the engaging member maintains this small concentrated point of contact in sustained operations with resulting wear causing minimum degradation (increase) of contact area, and minimum loss of effective cutting diameter. In some aspects, the engaging member maintains its shape in severe duty such as contact with gravel, rocks and other foreign objects in unimproved cutting conditions.

[0008] According to another aspect, there is provided a geometry that relocates the vegetation engaging point-of-contact and that is adaptable to most existing vegetation engaging member shapes, and thereby adaptable to most cutting machines. The new geometry moves the point of contact between the cutter and the vegetation from the longitudinal leading-edge axis of the engaging member to a point that is mid-plane horizontally and offset inboard from the outer tip of the cutter in the vertical plane. The specific amount of in-board offset from the outer tip in the vertical plane can be determined by the suitability to the type of machine and prevalent work. For example, it may be desirable to employ a smaller offset for finer work or lower powered machines and a greater offset for coarser work or higher-powered machines.

[0009] According to an aspect, there is provided a blade for use with vegetation, comprising a blade body. The blade body comprises a blade end, an attachment end, a first face and a second face. The first face and the second face are separated by a thickness of the blade body. The blade end comprises an end edge that is substantially parallel to an intended direction of travel of the blade body during use, and a blade edge adjacent to the end edge.
The blade edge comprises a concave recess that intersects with the end edge to define a contact point, wherein the contact point redirects at least a portion of the vegetation into the concave recess such that the concave recess and the contact point are maintained as the blade end erodes, the concave recess having an engagement surface that is flat and extends perpendicularly between and relative to the first face and the second face.

[0010] According to other aspects, the concave recess and the contact point may define a wedge shape or a conical shape relative to the intended direction of travel;
the concave recess and the contact point may define a contact edge positioned between the blade end and the attachment end, wherein the contact edge leads or is aligned with the blade end in the intended direction of travel; the contact point may comprise a flat surface that is perpendicular to the intended direction of travel, and in the direction of the length of the blade, the contact point may be no more than twice the thickness of the blade; the contact point and the concave recess may be defined by a profile that experiences wear consistently across the contact point and the concave recess, such that the profile remains substantially constant during a lifecycle of the blade; there may be a secondary concave recess adjacent to the concave recess that intersects with a secondary end edge to form a secondary contact point; there may be a plurality of blade bodies, and a vegetation blade that comprises a blade guide and an elongate blade carrier that circumscribes, and travels along, the blade guide, the attachment end of each blade body being attached to the elongate blade carrier, where the cutter guide may comprise a linear motion blade guide and the attachment end of each blade body may comprise a pivoting attachment point.

[0011] According to an aspect, there is provided a cutter element for use with vegetation, comprising a cutter body comprising a contact end and an attachment end spaced behind the contact end. The contact end comprises one or more flat segments that surround a recessed section. The one or more flat segments are in a plane that extends perpendicularly to an intended direction of travel of the cutter body.

[0012] According to another aspect, the contact end may comprise four flat segments equally spaced about the recessed section, or a circular flat segment that circumscribes the recessed section; each flat segment may comprise three or four surrounding edges; the cutter end may have a leading profile that is circularly symmetrical, the one or more flat segments have a width in a direction from a center of the contact end, and the recessed section has an angle immediately adjacent to the flat segments, where the width of the flat segments and the angle of the recessed section may be selected such that the leading profile of the cutter end experiences wear consistently across the cutter end such that the profile remains substantially constant during a lifecycle of the cutter.

[0013] In other aspects, the features described above may be combined together in any reasonable combination as will be recognized by those skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
FIG. 1 is a side elevation view of a prior art cutter blade.
FIG. 2 is a perspective view of a prior art cutter blade.
FIG. 3 is a side elevation view of a vegetation blade.
FIG. 4 is a perspective view of a vegetation blade.
FIG. 4a is a detailed perspective view of a blade portion of the vegetation blade.
FIG. 5 is a perspective view of an alternative vegetation blade.
FIG. 5a is a detailed perspective view of a blade portion of the vegetation blade.
FIG. 6 and 7 are views of a worn prior art cutter blade.
FIG. 8 is a perspective view of a vegetation blade for a linear cutter.
FIG. 9 is a side elevation view of a vegetation blade for a linear cutter.
HG. 10 is a perspective view of a linear cutter.
FIG. 11 is a perspective of a cutter element for a rotary style vegetation cutter.
HG. 12 and 13 are perspective views of alternative cutter elements.
DETAILED DESCRIPTION

[0015] A vegetation blade will now be described with reference to FIG. 3 through 11. A
cutter element will then be described with respect to FIG. 11 ¨ 13.

[0016] It has been found that, typically, the outer most corner of the leading edge of the knife-edge wears more quickly than the rest of the knife-edge and the corner takes on a rounded profile that reduces the effective length of the overall cutter, and thus reduces the effective cutting distance that can be contacted. In addition, the shaped knife-edge and particularly the leading corner of the knife edge inherently has a greatly reduced contact surface area, resulting in greatly increased wear caused by impact loading to the knife when the knife contacts a hard object. The wear can happen so quickly that some operators choose to ignore the degraded performance and in essence simply rely on the resulting dulled once-knife-edge blade to contact the vegetation and separate the stem in what may be more accurately described as a clubbing/beating action rather than a cutting or even abrading action. The result is degradation in the quality of the finished product and the efficiency of the operation, or an increase in the overall cost of operation related to replacing the blades as soon as they are worn.

[0017] The blade described herein relates to devices that break apart vegetative stems for heavy duty vegetation control. The device geometry is defined so as to relocate the impacting surface that engages the vegetation, to more represent an abrading hammer action rather than the traditional knife action. This results in a longer useable (and un-maintained) wear life. It also self-maintains a desirable shape and has greater resistance to impact with undesirable objects such as rocks.

[0018] As shown in FIG. 3 ¨ 5, vegetation blade 10 has a blade body 12 with a blade end 14 and an attachment end 16. The blade end 14 has an end edge 18 that is substantially parallel to an intended direction of travel of the blade body during use. As shown, the end edge 18 is slightly curved, which corresponds to a rotary movement. The end edge 18 may also be flat, which corresponds to a tangent of the direction of movement. The end edge 18 may also be recessed slightly from the direction of movement, although doing so may weaken the blade if it is recessed significantly. The blade end 14 comprises a concave recess 20 that intersects with the end edge 18 and defines a contact point 22, wherein the contact point 22 redirects at least a portion of the vegetation into the concave recess 20 such that the concave recess 20 and the contact point 22 are maintained as the blade end erodes due to contact with vegetation and other obstacles.

[0019] As shown, the concave recess 20 is a continuous curve, although other shapes may also be used. However, it is likely that, as the concave recess 20 erodes, it will approximate a continuous curve. The concave recess 20 as shown has an angled surface 24 immediately adjacent to the contact point 22 such that the concave recess 20 and the contact point 22 define a wedge shape relative to the direction of travel of the blade body 12 during use. In other configurations of vegetation blade 10, concave recess 20 and contact point 22 may instead define a conical shape relative to the intended direction of travel of blade body 12 during use. It will be understood that the shape defined by concave recess 20 and contact point 22 will be determined, at least in part, but the ratio between the width of contact point 22 in the direction of the length of blade 10 and the thickness of blade 10.
For example, for a ratio having a width of point 22 that is similar to the thickness of blade body 12, the shape defined by concave recess 20 and contact point 22 may be conical, while for a ratio having a width of point 22 that is closer to twice the thickness of blade body 12, the shape defined by concave recess 20 and contact point 22 may instead be wedge shaped.

[0020] There may also be a contact edge 26 positioned between the blade end 14 and the attachment end 16. As shown, the contact edge 26 leads or is aligned with the blade end 14 in the intended direction of travel. This may be used to protect the blade end 14 by pushing the blade out of the way if an obstacle, such as a rock, is encountered. This is particularly useful if the attachment end 16 is a pivoting attachment. As will be understood, the thickness of the blade body means it will inherently have a face along the edge of the body. In one example, the face is perpendicular to the side faces, particularly if the blade is formed by stamping or cutting from sheet material. As the blade is used, this edge may erode and become rounded.

[0021] FIG. 1 and 2 show a conventional knife-edge style of vegetation engaging blade.
The blade 10 is typically mounted on a moving holder and is allowed to additionally pivot about an axle placed through attachment end 16. The momentum of travel keeps the cutting edge 21 of the blade exposed to the target vegetation unless an obstacle is encountered by the cutting edge at which time the blade's momentum is overcome by the resistance of the obstacle and the blade is allowed to deflect out of the path because of the freely pivoting action afforded by attachment end 16. The knife edge 21 typically has one or more machined bevels applied longitudinally down the length of the leading edge. This knife edge treatment is also usually applied to the opposite edge so that the blade can either be used in the opposite direction, or can also be removed and reversed to offer a second wearing edge to the original direction of travel.

[0022] Because of the dynamic interaction between the force of momentum within the moving vegetation engaging blade, and the constant resistance of a stationary foreign object such as a rock, the blade 10 does not necessarily completely deflect out of the path by rotating on an axle about attachment end 16. Instead, the entire longitudinal knife edge 21 becomes a sliding point of contact between the forces of the knife's momentum and the resisting force of the rock or foreign object.

[0023] FIG. 3 & 4 illustrate how the new geometry would be applied to the same vegetation engaging blade profile as that used in FIG. 1 and 2. No longitudinally machined "knife-edge" is introduced to the blank 26, which is left unmodified. Instead a relief gullet 20 is introduced to the leading face of the blade near the blade tip, which isolates an impacting surface 22 that is the first surface to contact the vegetative stem. Thus, all the energy stored in the moving blade is concentrated on and transferred by the relatively small area of contact point 22 shown in FIG. 4a to the stem which abrades and separates the stem.

[0024] If the abrading blade in FIG. 3 and FIG. 4 encounters a foreign object such as a rock, or the operator forces the engaging member into an object too aggressively then the interaction of the forces between the momentum of the blade and the resisting object cause the blade to deflect by rotating on an axis through attachment end 16 as would also normally be the case as shown in HG. 1 and HG. 2.

[0025] The difference is that where a thin knife profile 21 shown in FIG. 1 and FIG. 2 would have to absorb the resulting force over a very concentrated area thus causing rapid deformation and wear of knife profile 21, instead the blunt face 26 shown in HG. 3 and FIG.
4 absorbs the resultant force over a greater surface area with minimal degradation to the overall profile.

[0026] The primary benefit of having a blunt face 26 rather than a knife edge 21 may be that when an object is encountered that presents a resistant force greater than the force that the hammer blade is able to exerted, the blunt face 26 dissipates the force much more effectively than the knife edge 21 and better serves to protect the primary contact point 22 from rock damage. This may contribute greatly to the useful life of the cutter. Besides ensuring the abrading action occurs at the tip, the gullet 20 may also serve to allow clearing of debris from the area being separated.

[0027] Additionally, FIG. 3 and FIG. 4 illustrate that it may be desirable to duplicate the features 26, 20 and 22 on the opposite edge of the vegetation engaging member to allow for rotation of the device in the opposite direction, or to allow for removing the blade and re-installing it with the opposite face forward.

[0028] FIG. 5 illustrates the result of wear to the abrasive impacting surface 22. As the edges 23 become worn, the concave recess, or gullet 20 ensures that the edges of the cutting face 22 wear relatively uniformly 23 resulting in the abrasive impacting face 22 being transformed into a focal point 22 where the abrading force that engages the vegetation is concentrated on a small area. This concentration of force enhances the abrading action. The natural continued erosion of the edges and resulting shoulders 23 maintains the shape of the contacting point 22 which is very effective in separating vegetative fibres, especially of woody vegetation.

[0029] In order to cause the wear to occur evenly along the length of the blade surface, the dimensions may be designed to account for the hardness and thickness of the blade. In many cases, the width of point 22, which is preferably a flat surface that is perpendicular to the intended direction of travel, toward blade end 14 will be no more than twice the thickness of blade body 12, and preferably around the same as the thickness of blade body 12. As such, it may be possible to design contact point 22 and concave recess 20 with a profile that experiences wear consistently thereacross, such that the profile remains substantially constant during a lifecycle of the blade.

[0030] Because the point is centred in the base material, when the point does encounter a rock, the abrading surface 22 is far less susceptible to breakage than its knife-edge counterpart. Additionally, continual wear occurs more rapidly at the sides 23 than at the center, and thus while point 22 recedes into the base material, the wearing surfaces 23 recede at the same rate, resulting in the overall shape of 22 being maintained over time. Engaging the member in more highly abrasive conditions only serves to amplify this feature as compared to the resulting wear pattern evidenced on the knife-edged cutters as illustrated in FIG. 6 and 7.

[0031] FIG. 6 and 7 illustrate the typical wear pattern of the conventional knife. The lack of a specific point of applied cutting force 22 and controlled wear shoulders 23, causes the end of the conventional knife edge 21 to become a sliding wear point resulting in undue abrasion to the knife tip and excessive rounding of the cutter. The result is a significant loss of mass of material and thus further loss of inertial effectiveness. As pointed out earlier, when a rock is encountered, the entire knife edge 21 becomes the line of force where the cutter deflects the force of the rock and rapidly wears the cutting edge rather than preserving it.

[0032] In addition, the wear patterns evidenced in FIG. 5 result in retaining more of the original overall length of the engaging member, which retains more of the original mass of the member at the tip. Since these types of engaging members are typically mounted so as to be free to pivot about attachment end 16 (as shown in FIG. 1), this mass retention minimizes the in-board shift of the original location of the moment arm of the member.
Prolonging the retention of mass and thus minimizing the in-board shift of the moment arm serve to maintain the original force available to be applied to the vegetative stem. In contrast, the evidenced wear pattern of the typical knife-edge blade, illustrated in FIG. 6 and FIG.
7, serves to reduce the outboard mass and thus shifts the moment arm of the member in-board, causing degradation of the force available to be applied to the vegetative stem. There is significant increase in efficacy because of retention of mass at the tip of the cutter.

[0033] It should be noted that the new geometry may provide significant savings in not having to initially machine the leading edge(s) of the knife to introduce the bevel(s), nor having to re-machine a new bevel on a worn blade.

[0034] Of additional note is that this same geometric principle can be applied to cutters that primarily function in a linear or reciprocating linear motion, FIG. 8 and FIG. 9, and while the effects of momentum from angular velocity would not apply, the same self-sharpening characteristics and resistance to rock damage would apply. FIG. 10 shows a linear motion cutter using the blades shown in FIG. 8 and 9.

[0035] Referring now to FIG. 11, there is shown a cutter element, generally indicated by reference number 200, which is designed to be used with a drum-style cutter, an example of which is described in U.S. patent no. 7,222,808 (Edwards) entitled "Mulcher with improved tooth design". Cutter 200 has a cutter body 202 with a contact end 204 and an attachment end 206 that allows cutter 200 to be attached to a cutter machine. Attachment end 206 is spaced behind contact end 204, such that contact end 204 leads cutter body 202 in use. The size and shape of attachment end 206 may vary, depending on the equipment with which it is intended to be used. Contact end 204 has one or more flat segments 208 that surround a recessed section 210. Flat segments 208 are in a plane that extends perpendicularly to an intended direction of travel of the cutter body 202, such that, similar to the blade described above, a flat, abrading surface is presented to the vegetation. As shown in FIG. 11 and 12, contact end 204 may be made of separate, discrete flat surfaces 208. The difference between these embodiments is that flat surfaces 208 have a different surface area, and a different number of edges. In another example, referring to FIG. 13, contact end 204 may have a single flat surface 208 that circumscribes recessed section 210 in a circle. Other shapes, such as a square surface 208 that circumscribes recessed section 210, or other patterns such as more or fewer flat surfaces 208 than those shown in FIG. 11, may also be possible.
Preferably, contact end 204 is made circularly symmetrical, but this may not be the case in all embodiments. A
mounting hole 212 may be provided through attachment end 206 toward contact end 204.
Mounting hole 212 is provided to attach cutter element 200 to a holder (not shown).

[0036] As with the blade described above, cutter body 202 is preferably designed to wear evenly, such that it presents a consistent profile throughout its expected life. In order to do so, the width of flat surface 208 in a radial direction measured from the center of contact end 204, and the angle of recessed section 210, immediately adjacent to flat segments 208 may be designed to ensure that flat segments 208 redirect vegetation in a way that causes recessed section 210 to wear at the same rate as flat segments 208, which will become rounded as they begin to wear.

[0037] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.

[0038] The scope of the following claims should not be limited by the preferred embodiments set forth in the examples above and in the drawings, but should be given the broadest interpretation consistent with the description as a whole.

Claims (16)

What is Claimed is:

1. A blade for use with vegetation, comprising:
a blade body comprising:
a blade end, an attachment end, a first face, and a second face, the first face and the second face being separated by a thickness of the blade body, the blade end comprising an end edge that is substantially parallel to an intended direction of travel of the blade body during use, and a blade edge adjacent to the end edge;
wherein the blade edge comprises a concave recess that intersects with the end edge to define a contact point, wherein the contact point redirects at least a portion of the vegetation into the concave recess such that the concave recess and the contact point are maintained as the blade end erodes, the concave recess having an engagement surface that is flat and extends perpendicularly between and relative to the first face and the second face.

2. The blade of claim 1, wherein the concave recess and the contact point define a wedge shape relative to the intended direction of travel.

3. The blade of claim 1, wherein the concave recess and the contact point define a conical shape relative to the intended direction of travel.

4. The blade of claim 1, wherein the concave recess and the contact point define a contact edge positioned between the blade end and the attachment end, wherein the contact edge leads or is aligned with the blade end in the intended direction of travel.

5. The blade of claim 1, wherein the contact point comprises a flat surface that is perpendicular to the intended direction of travel.

6. The blade of claim 5, wherein, in the direction of the length of the blade, the contact point is no more that twice the thickness of the blade.

7. The blade of claim 1, wherein the contact point and the concave recess are defined by a profile that experiences wear consistently across the contact point and the concave recess, such that the profile remains substantially constant during a lifecycle of the blade.

8. The blade of claim 1, comprising a secondary concave recess adjacent to the concave recess, the secondary concave recess intersecting with a secondary end edge to form a secondary contact point.

9. The blade of claim 1, further comprising a plurality of blade bodies, and a vegetation blade that comprises a blade guide and an elongate blade carrier that circumscribes, and travels along, the blade guide, the attachment end of each blade body being attached to the elongate blade carrier.

10. The blade of claim 9, wherein the blade guide comprises a linear motion blade guide.

11. The blade of claim 9, wherein the attachment end of each blade body comprises a pivoting attachment point.

12. A cutter element for use with vegetation, comprising:
a cutter body comprising a contact end and an attachment end spaced behind the contact end, the contact end comprising one or more flat segments that surround a recessed section, the one or more flat segments being in a plane that extends perpendicularly to an intended direction of travel of the cutter body.

13. The cutter element of claim 12, wherein the contact end comprises four flat segments equally spaced about the recessed section.

14. The cutter element of claim 12, wherein the contact end comprises a circular flat segment that circumscribes the recessed section.

15. The cutter element of claim 13, wherein each flat segment comprises three or four surrounding edges.

16. The cutter element of claim 13, wherein:

the contact end has a leading profile that is circularly symmetrical;
the one or more flat segments have a width in a direction from a center of the contact end;
the recessed section has an angle immediately adjacent to the flat segments;
and the width of the flat segments and the angle of the recessed section are selected such that the leading profile of the contact end experiences wear consistently across the contact end such that the leading profile remains substantially constant during a lifecycle of the cutter element.