Note: Descriptions are shown in the official language in which they were submitted.
CA 02616737 2008-01-02
MOWER KNIVES WITH STAGGERED SERRATIONS
Field of the Invention
This application claims priority to U.S. Provisional Application Serial No.
60/885,860 filed January 19, 2007.
This invention relates to reciprocating knives for cutting stalk-like crop
like grass or
grain. More particularly, it relates to reciprocating knives having knife
sections
with serrated cutting edges, wherein the serrations of one knife are staggered
with
respect to the serrations of an adjacent knife.
Background of the Invention
Reciprocating cutter bar assemblies have been used to cut crops such as wheat,
oats, rye, barley and soybeans for over a century. Reciprocating cutter bar
assemblies are typically constructed of a number of knives fixed in a row to a
knifeback that is driven in reciprocation.
Stationary guard fingers (also called guard points or guard tips) are mounted
adjacent to the knives such that when the bar is driven in a reciprocating
motion,
the knives on the bar engage the stationary guard fingers to cut the crop
therebetween.
Prior art knives generally comprise a rectangular base for mounting the knife
to
the reciprocating bar and have forward trapezoidal or triangular cutting
sections
with cutting edges that are obliquely arranged to the forward direction of
travel.
Knives with single cutting sections have been used as well as double knives
with
twin cutting sections arranged side by side. Usually, the length of all knives
in the
forward direction is identical, but also knives with staggered forward tips
have
been described. The cutting edges are smooth or serrated, i. e. provided with
small notches for improving the cutting action, and thus comprise a number of
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troughs and peaks arranged in an altemating fashion.
In the prior art, the peaks of the serrated cutting edges of all knives are
lying on
parallel lines extending transversely to the forward direction, and the
troughs of
the cutting edges of all knives are also arranged on parallel lines extending
transversely to the forward direction.
One problem with this arrangement is excessive wear on small localized areas
of
the guard fingers and of the cutting section of the knife, since wear mainly
appears at the peaks of the serrations. This is particularly a problem at
cutter bar
assemblies with a double cut configuration, at which more than one cutting
section
passes over or through a single guard finger.
It is an object of the invention to provide a twin knife having a cutting
section with
serrated cutting edges that provides an extended lifetime of a guard finger
that
interacts with the knives and of the knives.
Summary of the Invention
A twin knife configured to be mounted on a reciprocating knifeback of a
reciprocating cutter bar assembly comprises a first cutting section and a
second
cutting section. Both cutting sections extend in a forward direction and have
at
least one lateral face with a serrated cutting edge. The cutting edges
comprise a
plurality of first troughs and first peaks that are arranged in an alternating
manner.
Bases are fixed to the rearward ends of the cutting sections and have at least
one
aperture for receiving a connector to couple the base to the reciprocating
knifeback. The serrations of the first cutting edge of the first cutting
section and
the serrations of the second cutting edge of the second cutting section are
arranged in a staggered fashion. Thus, in a state when the first base and the
second base are mounted to the bar, the first troughs are offset in the
forward
direction from the second troughs and the second peaks are offset in the
forward
direction from the first peaks.
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Hence, the first cutting edge and the second cutting edge are interacting
during
the cutting or mowing operation with different locations of a counteracting
shearbar such as a guard finger. Wear of the knives and of the guard finger is
thus reduced and their lifetime is increased.
In a preferred embodiment of the invention, the first cutting edge of the
first cutting
section and the second cutting edge of the second cutting section are arranged
on
the same (e. g. left or right) side of the longitudinal center plane of the
cutting
sections. Thus, both said cutting edges interact with the same face of a
shearbar
or guard finger.
Preferably, each of the cutting section comprises two cutting edges. Hence,
the
first cutting section has a second lateral face with a third cutting edge. The
third
cutting edge comprises a plurality of third troughs and third peaks that are
arranged in an alternating manner. Also, the second cutting section has a
second
lateral face with a fourth cutting edge. The fourth cutting edge comprises a
plurality of fourth troughs and fourth peaks that are arranged in an
alternating
manner. The serrations of the fourth edge and those of the third edge are
arranged in a staggered manner. Thus, the cutting sections can have a
trapezoidal or triangular shape with two lateral cutting edges and a pointed
or
flattened tip, the latter extending transversely to the forward direction. The
described reduced wear is achieved on both sides of the guard finger and all
four
cutting edges of both knives.
In an embodiment, the troughs of the first cutting section can be aligned with
the
peaks of the second cutting section and vice versa, i. e. an imaginary line
extending through a first trough and a third trough intersects a second peak
and a
fourth peak, and an imaginary transverse line extending through a first peak
and a
third peak intersects a second trough and a fourth trough. In other words, the
third troughs and third peaks are aligned in the forward direction with the
first
troughs and first peaks of the first cutting edge of the first cutting
section, while the
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fourth troughs and fourth peaks are aligned in the forward direction with the
second troughs and second peaks of the second cutting edge of the second
cutting section. It should however be noted that it would be possible to align
a first
trough with a third peak and a second peak and a fourth trough (and a first
peak
with a third trough and a second trough and a fourth peak), since staggering
the
serrations on identical lateral sides of the cutting sections is the main
feature of
the present invention. Also, staggering the serrations by smaller values as
previously described lies within the scope of the present invention. For
example,
the troughs of the first cutting edge can be transversely aligned in the
forward
direction with locations lying between the troughs and peaks of the second
cutting
edge.
The knife arrangement comprising first base, the second base, the first
cutting
section and the second cutting section can be produced (e. g. cast or cut) as
a
single, unitary piece. Alternatively, the first cutting section and the first
base are
formed as a single part, and the second cutting section and the second base
are
another, independent single part.
In a preferred embodiment, a forward tip of the first cutting section is in
the
forward direction offset from a forward tip of the second cutting section. In
another embodiment, both tips can however be aligned.
The twin knife and the reciprocating cutter bar assembly can be used on any
type
of harvesting machines, for example on platforms for combines or grass mowers.
These and other objects, features and advantages of the present invention will
become apparent to one skilled in the art upon reading the following detailed
description in view of the drawings.
Brief Description of the Drawin-gs
Figure 1 is a plan view of a combine with a header having a reciprocating
cutter
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bar assembly in accordance with the present invention.
Figure 2 is a fragmentary detail plan view of the header of Figure 1 showing a
plurality of knives mounted in a row and guard fingers cutting against of the
reciprocating knives of the cutter bar assembly of Figure 1. The knife
sections are
shown in simplified form without serrations for clarity of illustration.
Figure 3 is a plan view of a representative twin knife of the plurality of
knives of
Figure 2 with all components of the header removed except the reciprocating
bar
to which the representative twin knife is mounted and the guard finger against
which the cutting sections of the representative twin knife cut the crop
matter.
Figure 4 is a plan view of another embodiment of a twin knife of the plurality
of
knives of Figure 2.
Description of the Preferred Embodiment
Referring now to Figure 1, a combine 100 is shown having a header 102 coupled
thereto, that is configured to be driven through an agricultural field in a
forward
direction "F" of the combine to cut crop material. In the following, all
directional
references, like forward, left, right, and lateral, are given with respect to
the
forward direction of combine 100.
Header 102 has an elongate reciprocating cutter bar assembly 104 that extends
along a forward edge of the header 102 to engage and cut crop plants as the
combine 100 moves in the forward direction "F" through the field.
Figure 2 is a detailed view of the right end of header 102 showing details of
the
reciprocating cutter bar assembly 104 which includes a plurality of twin
knives 106
that are mounted in a long row to a reciprocating bar or knifeback 108.
Reciprocating cutter bar assembly 104 also includes stationary guard fingers
110
that extend forward and are disposed adjacent to each twin knife 106 such that
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least two adjacent cutting sections of the twin knives 106 cut against one
side of
the guard finger 110 during a complete reciprocation cycle.
Figure 3 is a plan view of a double knife 106. Each double knife 106 has a
common, unitary base 112 to which two cutting sections 114, 116 are fixed. The
cutting sections 114, 116 are generally triangular and each has two lateral
faces
with cutting edges 118, 120, 122, 124 respectively. In particular, the first
cutting
section 114 has a first cutting edge 118 at the right hand side of its
longitudinal
center plane 134 and a third cutting edge 120 at the left hand side of its
longitudinal center plane 134. Likewise, the second cutting section 116 has a
second cutting edge 122 at the right hand side of its longitudinal center
plane 136
and a fourth cutting edge 124 at the left hand side of its longitudinal center
plane
136.
Base 112 has several apertures 130 that receive bolts 132. Bolts 132 are
threaded into the reciprocating knifeback 108 to fix the twin knife 106
thereto in
parallel relation along the entire length of the reciprocating knifeback 108.
The
first cutting section 114 and its associated part of the base 112 behind it
define a
first knife 138, while the second cutting section 116 and its associated part
of the
base 112 behind it define a second knife 140.
The cutting edges 118, 120 of the first cutting section 114 are shorter than
the
cutting edges 122, 124 of the second cutting section 116. The cutting edges
118,
120 terminate at a tip 126 of the first cutting section 114. Cutting edges
122, 124
are longer than the cutting edges 118, 120 and terminate at a tip 128 of the
second cutting section 116. The tip 126 of the first cutting section 114 is
offset
behind (i.e. to the rear of) the tip 128 of the second cutting section 116.
All four cutting edges 118, 120, 122, 124 are serrated and thus comprise a
number of peaks 142 and troughs 144 arranged in an alternating manner. The
peaks 142 of the first cutting edge 118 are - in the forward direction F -
aligned
with the peaks 142 of the third cutting edge 120, hence two peaks 142 having
the
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same forward position are positioned on a transversely extending imaginary
line
146. This imaginary line 146 also (at least approximately) extends through two
troughs 144 of the second cutting edge 122 and of the fourth cutting edge 124.
The two troughs 144 of the second cutting edge 122 and of the fourth cutting
edge
124 are also aligned in the forward direction.
Analogously, the troughs 144 of the first cutting edge 118 are - in the
forward
direction F - aligned with the troughs 144 of the third cutting edge 120,
hence two
troughs 144 having the same forward position are positioned on a transversely
extending imaginary line 148. This imaginary line 148 also (at least
approximately) extends through two peaks 142 of the second cutting edge 122
and of the fourth cutting edge 124. The two peaks 142 of the second cutting
edge
122 and of the fourth cutting edge 124 are also aligned in the forward
direction.
The stroke of the knifeback 108 is such large that both cutting sections 114,
116
pass below and/or above the guard finger 110, which acts as a shearbar to cut
the
crop. Since the serrations of both cutting sections 114 and 116 are offset or
staggered by half a serration tooth pitch, crop caught by the second cutting
section 116 is mainly cut between the peaks 142 of the second cutting section
116
and the guard finger 110 at a location 152 on line 148 (and all other
imaginary
lines connecting forwardly aligned peaks 142 of the second cutting section
116),
while crop caught by the first cutting section 114 is mainly cut between the
peaks
142 of the first cutting section 114 and the guard finger 110 at a location
150 on
line 146 (and all other imaginary lines connecting forwardly aligned peaks 142
of
the first cutting section 116) on both sides of the guard finger 110 due to
the
reciprocating motion of the knifeback 108. Thus, the cutting action is more
evenly
distributed along the length of the guide finger 110 and wear both of the
guide
finger 110 as well as of the cutting sections 114, 116 is reduced over the
prior art.
In the embodiment of Figure 4, elements corresponding to the elements of
Figure
3 have been assigned the same reference numerals. The main difference is that
separate bases 11 2a, 11 2b have been assigned to the cutting sections 114,
116.
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The first knife 138 and the second knife 140 are hence separately mounted to
the
knifeback 108.
Having described the preferred embodiment, it will become apparent that
various
modifications can be made without departing from the scope of the invention as
defined in the accompanying claims.
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