A CUTTING LBADE AND A CUTTING ASSEMBLY

Abstract

This specification describes improvements to cutting blades and a cutting blade assembly. In some forms the cutting blade includes an upturn with an upturn radial angle which is non-parallel to a reference axis.

Claims

1-68. (canceled)

69. A cutting blade for use in a cutting assembly, wherein the cutting blade includes: a body, wherein the body includes a first portion having an attachment point which is configured to pivotably attach the cutting blade to a mounting beam, a cutting portion having a cutting edge, and a step that separates the first portion and the cutting portion from each other, and wherein the step is orientated at an angle to a substantially horizontal plane in which the first portion lies; wherein the cutting edge is oriented at a rake angle which is the angle between a rake angle reference axis that extends along a leading edge of the cutting blade and a cutting edge axis that extends along at least a part of the cutting edge, and further wherein the rake angle is in the range of substantially 4° to substantially 41°.

70. A cutting blade for a cutting assembly, wherein the cutting blade includes: a body, wherein the body includes a first portion having an attachment point which is configured to pivotably attach the cutting blade to a mounting beam, a cutting portion having a cutting edge, and a step that separates the first portion and the cutting portion from each other, and wherein the step is orientated at an angle to a substantially horizontal plane in which the first portion lies; wherein the cutting edge is oriented at a rake angle which is the angle between a rake angle reference axis and a cutting edge axis, wherein the rake angle reference axis extends from a centre of rotation of the cutting blade in use to an outer tip of the cutting edge, wherein the cutting edge axis extends along at least a part of the cutting edge, and further wherein the rake angle is in the range of substantially 0° to substantially 30°.

71. The cutting blade of claim 70, wherein the cutting blade further comprises an upturn that has a forward-most edge and a rear edge, and further wherein the rear edge has an outer tip, and wherein an upturn radius axis extends from the centre of rotation of the cutting blade in use to the outer tip.

72. The cutting blade of claim 71, wherein the outer tip is substantially 590 mm from the centre of rotation in use when secured to the mounting beam.

73. A cutting blade for a cutting assembly, wherein the cutting blade includes: a body, wherein the body includes a first portion having an attachment point which is configured to pivotably attach the cutting blade to a mounting beam, a cutting portion having a cutting edge, and a step that separates the first portion and the cutting portion from each other, and wherein the step is orientated at an angle to a substantially horizontal plane in which the first portion lies; wherein the cutting edge is oriented at a rake angle which is the angle between a rake angle reference axis and a cutting edge axis, wherein the cutting edge axis extends along at least a part of the cutting edge, and wherein the rake angle reference axis extends from a centre of rotation of the cutting blade in use to an intersection point, the intersection point being the point of intersection between an axis that extends along the cutting edge and an axis that extends along a base edge of the cutting blade, and further wherein the rake angle is in the range of substantially 0° to substantially 30°.

74. The cutting blade of claim 73, wherein cutting blade comprises an upturn that has a forward-most edge and a rear edge, and further wherein an upturn radius axis extends from the centre of rotation to a second intersection point, the second intersection point being the point of intersection between an axis that extends along the rear edge and an axis that extends along the base edge.

75. The cutting blade of claim 74, wherein the second intersection point is substantially 590 mm from the centre of rotation in use.

76. The cutting blade of claim 73, wherein the base edge provides an outermost edge of the body.

77. The cutting blade of claim 69, wherein at least a part of a/the leading edge of the cutting blade is substantially parallel to a rotation axis that extends from the attachment point to the centre of rotation.

78. The cutting blade of claim 69, wherein at least a part of a/the leading edge of the cutting blade is substantially non-parallel to a rotation axis that extends from the attachment point to the centre of rotation.

79. The cutting blade of claim 69, wherein the upturn and the cutting edge are located on opposite sides of the body of the cutting blade.

80. The cutting blade of claim 69, wherein the cutting edge is provided on a forward edge of the cutting blade.

81. A cutting assembly including: the cutting blade according to claim 69, and the mounting beam.

82. The cutting assembly of claim 81, wherein the mounting beam has a first end and a second end, and wherein the cutting blade is attached at or towards the first end of the mounting beam.

83. The cutting assembly of claim 82, further comprises a second cutting blade which is attached at or toward the second end of the mounting beam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] One or more embodiments of the invention will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which:

[0082] FIG. 1 is a bottom view of a mower deck according to an embodiment of the present invention;

[0083] FIG. 2A is a perspective view of the cutting assembly according to an embodiment of the present invention;

[0084] FIG. 2B is an exploded view of FIG. 2A;

[0085] FIG. 3A is a perspective view of a cutting blade according to an embodiment of the present invention;

[0086] FIG. 3B is a top view of the cutting blade of FIG. 3A;

[0087] FIG. 3C is a bottom view of the cutting blade of FIG. 3A;

[0088] FIG. 4 is a view of a cutting blade through line A-A shown in FIG. 3B;

[0089] FIG. 5 is a further top view of the cutting blade of FIG. 3A;

[0090] FIG. 6A is a further top view of the cutting blade of FIG. 3A showing additional features of a cutting blade according to an embodiment of the present invention;

[0091] FIG. 6B is a further top view of the cutting blade of FIG. 3A showing additional features of a cutting blade according to an embodiment of the present invention;

[0092] FIG. 7A is a top view of a cutting blade according to an embodiment of the present invention;

[0093] FIG. 7B is a perspective view of the cutting blade of FIG. 7A;

[0094] FIG. 7C is a bottom view of the cutting blade of FIG. 7A;

[0095] FIG. 7D is a further view of FIG. 7A showing additional features of a cutting blade according to an embodiment of the present invention;

[0096] FIG. 7E is a further view of FIG. 7A showing additional features of a cutting blade according to an embodiment of the present invention;

[0097] FIG. 8A is a top view of a cutting blade according to another aspect of the present invention;

[0098] FIG. 8B is a perspective view of the cutting blade of FIG. 8A;

[0099] FIG. 9A is a top view of a cutting blade according to a second embodiment of the present invention;

[0100] FIG. 9B is a perspective view of the cutting blade of FIG. 9A;

[0101] FIG. 10A is a top view of a cutting blade according to a third embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0102] Cutting Assembly

[0103] Referring first to FIG. 1, showing a bottom view of a mower deck (100) which is indicated as (100). The mower deck (100) comprises a housing (102) and at least one baffle (103) that together form at least one cutting chamber (indicated as (104)). At least one cutting assembly (106) is mounted in the cutting chamber(s) (104).

[0104] In the embodiment of FIG. 1, the mower deck (100) includes three housings (102) and three cutting assemblies (106). However, the mower deck (100) may have any required number of cutting assemblies (106).

[0105] The cutting assemblies (106) shown in FIG. 1 are fling-tip cutting assemblies as are discussed in more detail below.

[0106] Each cutting assembly (106) is mounted to a rotor (108) which is in turn mounted to a drive system (not shown in the Figures). In use, the drive system (not shown) can rotate the rotor(s) (108) which in turn rotate the respective cutting assembly (106) to facilitate the mower deck (100) cutting grass. However, each cutting assembly (106) may be a blade (200) as is discussed below.

[0107] The housing (102) includes a support frame (not shown) in FIG. 1 which facilitates attaching the mower deck (100) to a prime mover such as a tractor (not shown in FIG. 1). Alternatively, the mower deck (100) may be provided in an autonomous mower (not shown in the Figures).

[0108] In the embodiment of FIG. 1 the mower deck (100) is provided as a single-deck mower. However, the mower deck (100) may also be part of a multi-deck mower having two or mower decks, each of which are equivalent to the mower deck (100).

[0109] Fling-Tip Cutting Assembly

[0110] Referring now to FIG. 2A which shows the cutting assembly (106) according to an aspect of the invention, and FIG. 2B which is an exploded view of FIG. 2A. The cutting assembly (106) is a fling-tip type cutting assembly having a mounting beam (110) and at least one cutting blade (120A), and preferably a second cutting blade (120B).

[0111] The cutting blades (120A, 120B) are attached to the mounting beam (110) using a fastener arrangement e.g. removably. In the illustrated embodiments, the fastener arrangement is a nut (151A, 151B) and bolt (155A, 155B) which extend through corresponding apertures (150A, 150B) in the mounting beam and apertures (136A, 136B) in the cutting blades (120A, 120B). The apertures (150A, 150B) provide attachments points at which the cutting blades (120A, 120B) are attached to the mounting beam (110).

[0112] Removable attachment of the cutting blades (120A, 120B) to the mounting beam (110) reduce the cost of part replacement and serviceability and improves ease of manufacturing.

[0113] However, other fastener arrangements are envisaged including, but not limited to, clamping, clipping or magnetic methods. It is also envisaged that the cutting blades are permanently attached to the mounting beam (110) such as by welding, or that they can be formed integrally to the mounting beam as is discussed in more detail below with reference to FIGS. 2A and 2B.

[0114] In the illustrated embodiment, the fastener arrangement allows the cutting blades (120A, 120B) to pivot freely or partially with respect to the mounting beam (110). Alternatively, the fastener arrangement may fixedly attach the cutting blades (120A, 120B) to the mounting beam (110) to substantially prevent rotation of the cutting blades (120A, 120B) with respect to the mounting beam (110).

[0115] The mounting beam (110) includes an aperture (112), and preferably a second aperture (114). The aperture(s) (112, 114) facilitate connecting the mounting beam (110) to the rotor (108). The attachment of the mounting beam (110) to the rotor (108) is achieved by at least one bolt (116) (as shown in FIG. 1) which extends through one of the apertures (112, 114) and into a corresponding aperture (not shown in the Figures) in the rotor (108). The advantage of having multiple points (112, 114) of connection between the mounting beam (110) and the rotor (108) is that it may assist in locking the mounting beam with respect to the rotor (108), which can be beneficial for performance of the mower deck (100).

[0116] The mounting beam (110) includes a centre aperture (indicated as 201) located at substantially the mid-point along the length of the mounting beam (110). The centre aperture (201) provides an alignment feature to assist in positioning the mounting beam (110) with respect to the rotor (108). For instance, the centre aperture (201) can receive a corresponding boss (not shown) or other alignment feature on the rotor (108).

[0117] The apertures (112, 114) are located substantially symmetrically on either side of the centre aperture (201). The centre aperture (201) is also the centre of rotation for the mounting beam (110), and therefore also the cutting blades (120A, 120B) when attached thereto.

[0118] It is also envisaged that only one cutting blade e.g. (120A) could be attached to the mounting beam (110). Alternatively, the mounting beam (110) may adopt any shape having any number of arms and cutting blades attached to the arms. For instance, it is envisaged that the mounting beam (110) may have three arms and three cutting blades could be attached thereto, one to each arm. In yet a further alternative embodiment, the mounting beam may have four arms and cutting blade is attached to each of the arms i.e. the cutting assembly has four cutting blades.

First Embodiment of a Cutting Blade

[0119] Referring now to FIG. 2B, together with FIGS. 3A, 3B and 3C which show additional views of the cutting blade (120A or 120B) illustrated in FIGS. 2A and 2B. As the cutting blades (120A, 120B) are identical to each other, only cutting blade (120A) will be described in detail.

[0120] The cutting blade (120A) includes a first portion (130) and a cutting portion (132) which are separated by a step (134). The aperture (136A) is provided in the first portion (130) and as discussed above facilitates attaching the cutting blade (120A) to the mounting beam (110).

[0121] When the cutting blade (120A) is rotationally aligned with the mounting beam (110) as shown in FIG. 2A, the cutting portion (132) is located farther away from the centre aperture (201) than the first portion (130). This provides the maximum possible moment arm for the cutting assembly (106) and may assist in reducing energy consumed to cut plant material.

[0122] The following discussion describes features of the cutting blade (120A) and cutting assembly (106) when assembled and with the cutting blade in the rotation orientation shown in FIG. 2A (amongst others). This will be referred to as “the reference position”. In the reference position, the longitudinal axis of the mounting beam (110) is substantially parallel to and colinear with, the longitudinal axis of the cutting blade (120A). It should be understood that in use the orientation of the cutting blade (120A) with respect to the mounting beam (110) may change according to various factors such as the weight of the cutting blade (120A), the amount of rotation of the cutting blade (120A) allowed by the fastener arrangement or other structure of the cutting assembly (106).

[0123] The cutting portion (132) includes a cutting edge (138) formed in a forward edge of the cutting portion (132). The cutting portion (132) lies on a substantially horizontal plane in use (not shown in the Figures) and has a rear edge (140) which is the edge of the cutting portion (132) distal from the cutting edge (138).

[0124] The cutting blade (120A) includes an upturn (142). The upturn (142) is orientated at an angle to the substantially horizontal plane (not shown) in which the cutting portion (132) lies and extends rearward of the rear edge (140) of the cutting portion (132). The rear edge (140) therefore provides a forward-most edge of the upturn (142).

[0125] The upturn (142) has a rear edge (143), an inner edge (144) and an outer edge (146).

[0126] The step (134) is orientated at an angle to a substantially horizontal plane (not marked in the Figures) in which the first portion (130) lies. Therefore, the first portion (130) is higher above the ground in use than the cutting portion (132). As a result, the cutting edge (138) is lower than the first portion (130) when the cutting assembly (106) is assembled and in use.

[0127] The arrangement and configuration of the step allows for a length of the cutting edge (138) that matches the travel speed of the prime mover, such that it decreases or eliminates the amount of uncut material remains after each pass of the mower.

[0128] Another advantage of the first portion (130) being higher above the ground than the cutting portion (132) is that there is a clearance between parts of the cutting assembly (106) and the ground. This ensures that components like bolts (116, 155A, 155B) or nuts (151A, 151B) that could project beyond the surface of the mounting beam (110) and the first portion (130) are less likely to come in contact with the ground when the mower deck (100) is in use.

[0129] The step (134) generally has a trapezoidal-shape which is defined by a leading edge (148) and a rearward edge (133) of the step (134). This is perhaps best seen in FIG. 3B. This shape may be particularly advantageous as it facilitates the other components having geometries required to provide the advantages of the present invention. However, other shapes for the step (134) are envisaged including a rectangle or parallelogram.

[0130] The first portion (130) has a leading edge (152). In the illustrated embodiment, the leading edges (148, 152) are substantially parallel to, and preferably substantially collinear to, each other when viewed from above. As illustrated in FIGS. 3B and 3C, the leading edges (148, 152) are parallel to an axis (149) when viewed from above.

[0131] In the embodiment shown in FIGS. 3A, 3B and 3C, the leading edges (148, 152) are substantially straight. In other embodiments, one or more of the leading edges (148, 152) may be curved.

[0132] The cutting blade (120A) includes a base edge (135) which is the outermost edge of the cutting blade (120A). In the embodiment illustrated in FIGS. 3A, 3B and 3C the base edge (135) is substantially straight. In other embodiments, the base edge (135) may have a curved shape.

[0133] The cutting blade (120A) has an upturn void (indicated by 153 in the Figures). The upturn void (153) is an area defined by the inner edge (144) of the upturn (142) and the rearward edge (133) of the step (134) that does not have any material i.e. it is “open”. An open void can reduce power consumption in use.

[0134] Referring now to FIGS. 4 and 5 which show additional aspects of the cutting blade (120A) and cutting assembly (106) according to the present invention.

[0135] FIG. 4 depicts the cutting blade (120A) perpendicularly from the plane A-A′ which may be seen in FIG. 3B.

[0136] The orientation and dimensions of the upturn (142) can be described with reference to an upturn vertical angle (154), an upturn radial angle (164) and an upturn vertical height (160).

[0137] In the embodiment illustrated in FIG. 4, the upturn vertical angle (154) is defined as the angle between a substantially horizontal plane (156) in which the cutting edge (138) lies and a plane (158) on which the upturn (142) lies.

[0138] In the embodiment of FIGS. 4 and 5, the upturn vertical angle (154) is preferably in a range of substantially 31° to substantially 49°, and is preferably substantially 40°.

[0139] The orientation of the upturn (142) may have an effect on the clipping spread and power consumption. The inventors have surprisingly found that the upturn radial angle (164), the upturn vertical angle (154), and the upturn vertical height (160) as described herein provide a desirable clipping spread while also optimising power consumption and having an acceptable level of clumping.

[0140] It is possible that a greater clipping spread may be obtained at other values for at least one of the upturn vertical angle (154), the upturn radial angle (164), and the upturn vertical height (160). However, the inventors have surprisingly found that other performance characteristics of the cutting blade (120A) and cutting assembly (106) deteriorate severely and below acceptable standards when values for at least one of the upturn vertical angle (154), the upturn radial angle (164), and the upturn vertical height (160) are outside of the ranges described herein. Accordingly, the invention balances competing factors which can affect performance of the cutting blade (120A) and cutting assembly (106).

[0141] For instance, clipping spread of the cutting blade (120A) and cutting assembly (106) can be evaluated by assessing mean residual spread, the lower the better. The inventors have found that for a specific range of upturn radial angles, the mean residual spread decreases as the magnitude of the upturn vertical angle (154) increases. However, the power consumption and clumping also increase as the magnitude of the upturn vertical angle (154) increases. The clipping spread may be improved only up to an upturn vertical angle (154) of substantially 49° before power consumption and clumping exceed acceptable limits. In addition, the magnitude of the upturn vertical angle (154) can be decreased to substantially 31° before clipping spreads falls below an acceptable level. Hence, having an upturn vertical angle (154) within the range of substantially 31° to substantially 49° provides an acceptable standard of clipping spread while also balancing other features for performance of the cutting blade (120A) and cutting assembly (106). In particularly preferred embodiments the upturn vertical angle is substantially 40°.

[0142] In addition, clipping spread and other performance characteristics depend not only on the upturn vertical angle, but a combination of all the geometric features of the cutting blade (120A).

[0143] The inventors have found that the upturn height (142) may be an important feature for the performance of the cutting blade (120A). In the embodiment of FIGS. 4 and 5, the upturn vertical height (160) is defined as the height of the upper most point (162) of the upturn (142) above a substantially horizontal plane in which the cutting edge (138) lies.

[0144] The inventors have found that the upturn height (142) may be an important feature for the performance of the cutting blade (120A). In the embodiment of FIGS. 4 and 5, the upturn vertical height (160) is defined as the height of the upper most point (162) of the upturn (142) above a substantially horizontal plane in which the cutting edge (138) lies.

[0145] In the embodiment of FIGS. 4 and 5, the upturn vertical height (160) is in the range of substantially 14 mm to substantially 22 mm, and preferably is substantially 15 mm. This range of heights may provide a desirable level of clipping spread while ensuring that blade design does not result in excess power consumption. This range also provides a reduction in clumping without exceeding acceptable limits in clipping spread.

[0146] The upturn radial angle (164) is defined with respect to a reference axis, e.g. an upturn radius axis (172) as illustrated in FIG. 5.

[0147] As can be seen in FIG. 5, the upturn radius axis (172) extends from an outer tip (174) of the upturn (142) to the centre aperture (201) i.e. the centre of rotation of the cutting assembly (106). In this embodiment, the upturn radial angle (164) is the angle between the upturn radius axis (172) and an upturn axis (166) which extends along the rear edge (140).

[0148] In the embodiment of FIG. 5, the upturn radial angle (164) is in the range of substantially −2° to substantially 20°, and preferably is substantially 11°.

[0149] In another embodiment (not shown in FIGS. 4 and 5), the outer edge of the upturn may be chamfered or rounded. In this embodiment, the upturn radius axis (172) extends from a virtual point (not indicated in the Figures) to the centre aperture (201). The virtual point may be located at the point of intersection between an axis that extends along the upturn rear edge (143) and an axis that extends from the base edge (135) which is the outermost edge of the cutting blade (120A).

[0150] The inventors have also surprisingly found that the orientation of the cutting edge (138) with respect to the other parts of the cutting blade (120A) i.e. the rake angle (179), can have an important effect on performance.

[0151] In FIG. 5, the rake angle (179) is defined as the angle between a cutting radius axis (176) that extends from the centre of rotation (201) to an outer edge (178) of the cutting edge (138) and an axis (180) which extends along the cutting edge (138).

[0152] In the embodiment of FIG. 5, the rake angle (179) is in the range of substantially 0° to substantially 30°, and preferably is substantially 12° The inventors have surprisingly found that having a rake angle in this range provides a cut which has a satisfactory level brooming. Increasing the rake angle above substantially 30° results in ineffective cutting with increased brooming (or an increase in uncut grass) exceeding acceptable levels. Having a rake angle of less than substantially 0° provides a less clean cut e.g. undesirable levels of brooming. As a result, the range of substantially 0° to 30° provides a balance for cut cleanliness and efficiency.

[0153] Alternative Description of a Cutting Blade

[0154] Referring now to FIGS. 6A and 6B which show further aspects of the cutting assembly (106) and cutting blade (120A or 120B) described above. Like numerals refer to like components.

[0155] In the embodiment of FIG. 6A, the upturn radial angle (161) is defined as an angle between the upturn axis (166) that extends along the rear edge (140) and an axis (149) that extends along the leading edge(s) (148 and/or 152). In this embodiment, the upturn radial angle is in a range of substantially 0° to substantially 30°, and preferably is substantially 20°.

[0156] It can be seen in FIG. 6A that the upturn axis (166) and therefore the rear edge (140) is orientated to define a taper in the cutting portion (132) in the direction of the step (134). Therefore, the cutting portion (132) has a generally trapezoidal-shape.

[0157] In the embodiment illustrated in FIG. 6A, the leading edge(s) (148, 152) is/are parallel to an axis (170) which extends from the centre aperture (201) to the attachment point (250). The axis (170) is best seen in FIG. 2A. Therefore, it should also be understood that the upturn radial angle (161) can also be described as an angle between the upturn axis (166) and the axis (170).

[0158] The orientation of the cutting edge (138) can be described by a rake angle (173). In the embodiment of FIGS. 6A and 6B, the rake angle (173) may be defined as the angle of the axis (180) that extends along the cutting edge (138) measured with respect to the axis (149) on which at least one of the leading edges (148, 152) lies.

[0159] In the embodiment of FIGS. 6A and 6B, the rake angle (173) is preferably in the range of substantially 4° to substantially 41°, and preferably is substantially 20°.

[0160] The advantages of having the upturn radial angle (161) and the rake angle (173) in the specified ranges in this alternative embodiment of the cutting blade (120A or 120B) are respectively the same as the advantages of the range of rake angles for the cutting blade (120A) described with reference to FIGS. 4 and 5 above.

[0161] One-Piece Cutting Assembly

[0162] Referring now to FIGS. 7A, 7B, 7C, 7D and 7E which show another embodiment of a cutting blade (300) according to an aspect of the invention. In this embodiment the cutting blade (300) is formed as a one-piece component in which cutting edges (302) and mounting beam (304) are formed from the same piece of material as each other. The advantage of a one-piece cutting assembly is reduction in cost of manufacturing.

[0163] In an alternate embodiment (not shown in FIGS. 7A, 7B, 7C, 7D and 7E), the mounting beam (304) could be formed with only a single cutting edge (302) located at one end of the mounting beam (304). In yet a further alternate embodiment (not shown in FIGS. 7A, 7B, 7C, 7D and 7E), the mounting beam (304) may have a shape generally described as a three-pointed star having three arms, with a cutting edge (302) formed in each of the arms. In yet a further embodiment (not shown in FIGS. 7A, 7B, 7C, 7D and 7E), the mounting beam (304) may have four arms having one cutting blade attached to each arm.

[0164] The cutting blade (300) includes apertures (306, 308) that are located symmetrically on either side of the centre (310) of the cutting blade (300). The apertures (306, 308) facilitate attaching the cutting blade (300) to the rotor (108) as illustrated in FIG. 1 and thereby providing a cutting assembly according to an aspect of the present invention.

[0165] The centre (310) is located at the centre of rotation of the cutting blade (300) in use and the cutting blade (300) is symmetrical about the centre (310).

[0166] The cutting blade (300) includes a first step (312) and a second step (314) that are located at distal ends of the mounting beam (304) to each other. The steps (312, 314) are orientated at an incline to a substantially horizontal plane in which the mounting beam (304) lies in use, and therefore the cutting edges (302) are located lower than the mounting beam (304).

[0167] The steps (312, 314) each have a generally trapezoidal shape and a leading edge (316) and a rear edge (318) as is best seen in FIG. 7A.

[0168] The steps (312, 314) join the mounting beam (304) to cutting portions (320). The cutting edges (302) are formed in the respective forward edges of the cutting portions (320).

[0169] Each cutting portion (320) includes a rear edge (322) which is the is the edge of the cutting portions (320) distal from the cutting edges (302). The cutting edges (302) and the rear edges (322) each lie in a substantially horizontal plane in use.

[0170] An upturn (324) extends away from the rear edges (322) so that the rear edges (322) provide a forward edge for the upturns (324).

[0171] Each upturn (324) includes an inner edge (326) and an outer edge (328).

[0172] The upturns (324) are orientated at an angle to a substantially horizontal plane (not marked in the Figures) in which the cutting edges (302) lie. The orientation of the upturn (324) with respect to the substantially horizontal plane can be described by an upturn vertical angle (not shown in FIGS. 7A, 7B, 7C, 7D and 7E). The upturn vertical angle of each upturn (324) is identical to the upturn vertical angle (154) of the cutting blade (120A) as illustrated in FIG. 4. In the embodiment of FIGS. 7A, 7B, 7C, 7D and 7E, the upturn vertical angle (not marked) may be in the range of substantially 31° to substantially 49°, and preferably is substantially 40°.

[0173] The height of the upturns (324) above the substantially horizontal plane in which the cutting edges (302) lie can be referred to as an upturn vertical height (not marked in the FIGS. 7A, 7B, 7C, 7D and 7E). The upturn vertical height of each upturn (324) of the one-piece cutting blade (300) is identical to the upturn vertical height (160) of the cutting blade (120A) as illustrated in FIG. 4. In the embodiment of FIGS. 7A, 7B, 7C, 7D and 7E, the upturn vertical height is in the range of substantially 14 mm to substantially 22 mm, and preferably is substantially 15 mm.

[0174] In addition to the upturn vertical angle and the upturn vertical height, the orientation of the upturns (324) with respect to the cutting portions (320) can be described by reference to an upturn radial angle (325). In the description of FIGS. 7A, 7B, 7C and particularly 7D, the upturn radial angle (325) is defined as an angle between an axis (327) that extends along a rear edge (322) and an axis (333) that extends along the leading edge(s) (316). In the embodiment of FIGS. 7A, 7B, 7C and 7D, the upturn radial angle (325) may be in the range of substantially 0° to substantially 30°.

[0175] Alternatively, as shown in the description of FIGS. 7A, 7B, 7C and particularly 7E, the upturn radial angle (331) may also be defined as an angle between an axis (335) that extends from the centre (310) to an outer tip of each of the upturns (324) and the axis (327) that extends along the rear edge (322). The range of the upturn radial angle (331) in this alternative description is substantially −2° to substantially 20°, and preferably is substantially 11°.

[0176] As can be seen in FIGS. 7A, 7B, 7C, 7D and 7E, the cutting blade (300) includes at least one, and preferably two, upturn voids which are indicated generally by (330). The upturn voids (330) are a region bounded at least partially by the inner edge (326) of the upturn (324) and the rear edge (318) of each of the steps (312, 314). The upturn voids (330) generally have a triangular shape and are unbounded on one side.

[0177] The orientation of the cutting edge (302) with respect to the cutting portion (320) is defined by a rake angle (340). In a first description of the rake angle (340), illustrated particularly in FIG. 7D, it is defined as an angle between the axis (333) that extends along the leading edge(s) (316) and an axis (342) that lies along the cutting edge (302). The range of the rake angle (340), according to this description, illustrated by FIG. 7D, is substantially 4° to substantially 41°, and preferably is substantially 20°.

[0178] Alternatively, the rake angle (345) may also be defined as an angle between an axis (347) that extends from the centre (310) to an outer edge of the cutting edge (302) and the axis (342) that lies along the cutting edge (302). The range of the rake angle (345), according to this alternate description, illustrated by FIG. 7E, is substantially 0° to substantially 30°, and preferably is substantially 12°.

Alternate Embodiment of a Cutting Blade

[0179] Referring now to FIGS. 8A and 8B which show an alternate embodiment of a cutting blade (400) according to an aspect of the present invention. The cutting blade (400) has some similarities to the cutting blade (120A, 120B) and therefore like numerals are used to refer to like features.

[0180] The cutting blade (400) has a cutting edge (138) which lies on a cutting edge axis indicated as (402) in FIGS. 9A and 9B. The cutting edge axis (402) is substantially parallel to, and preferably colinear with, an axis (404) which extends along the leading edge(s) (148 and/or 152). Accordingly, the cutting blade (400) has a rake angle of substantially zero.

Further Alternate Embodiment of a Cutting Blade

[0181] Referring now to FIGS. 9A and 9B which show a further embodiment of a cutting blade (500) according to an aspect of the present invention. The cutting blade (500) has some similarities to the cutting blade (120A, 120B) and therefore like numerals are used to refer to like features.

[0182] The rear edge (502) lies on an axis indicated as 504 in FIGS. 9A and 9B. The axis (504) is substantially parallel to the axis (149) which extends along the leading edge(s) (148 and/or 152).

Further Alternate Embodiment of a Cutting Blade

[0183] Referring now to FIG. 10 which shows a further embodiment of a cutting blade (600) according to an aspect of the present invention. The cutting blade (600) has some similarities to the cutting blade (120A, 120B) and therefore like numerals are used to refer to like features.

[0184] The cutting blade (600), in this embodiment does not include a step between a first portion (602) and a cutting portion (604) in which a cutting edge (606) is formed. Therefore, the first portion (602) and the cutting portion (604) lie in the same plane as each other.

[0185] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to”.

[0186] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

[0187] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0188] The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

[0189] Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0190] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention.

[0191] It will also be appreciated that various features of the embodiments described and illustrated herein may be combined to form yet further embodiments of the invention. These further forms of the invention are intended as being envisaged within the scope of the invention.