Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1
STUB GUARD FOR A SICKLE CUTTER SYSTEM
This invention relates generally to a stub guard for a sickle knife cutter
system for harvesting crop with improved cutting action.
BACKGROUND OF THE INVENTION
The present invention relates generally to a crop cutting device
comprising a frame structure arranged for forward travel over ground having a
standing crop thereon; a cutter bar secured to the frame structure and
extending
transversely across a front end of said frame structure; a plurality of knife
guards
mounted in spaced relation along said cutter bar and projecting forwardly
therefrom
in transverse alignment; each of said guards having an upwardly facing ledger
surface with opposed side edges thereof arranged to provide first and second
shearing edges; a sickle bar mounted in transversely extending position and
being
driven for reciprocating movement relative to said knife guards; the sickle
bar having
a plurality of knife blades mounted thereon for movement therewith; each of
the knife
blades having a cutting surface for passing across the ledger surface of the
knife
guards and an opposed surface; each of the knife blades having two side
cutting
edges which are beveled from the opposed surface to the cutting surface to
cooperate with said shearing edges of said knife guards; the sickle bar being
driven
to carry the knife blades back and forth between the knife guards.
It is well known that many sickle knives of this general type include a
conventional or pointed guard where the guard is formed as an integral element
which includes a base piece attached to the cutter bar and defining the ledger
surface and a nose piece projecting forwardly from the ledger surface in front
of the
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front edge of the blade which is generally pointed at a leading end so as to
separate
the crop to each side of the guard. This nose piece also stands up in front of
the
ledger surface to protect the front edge of the blade and includes a
rearwardly
extending shelf over the ledger surface which forms a slot with the ledger
surface
through which the blade passes. Guards of this type include separate hold down
members between the guards which apply downward pressure on the cutter bar to
press the blades against the ledger surface.
Pointed guards generally feature a point with a cut slot that the sickle
blades reciprocate in and out of. Various types of hold-down arrangement are
used
to apply pressure to the sickle to keep its shearing surface in close contact
with the
guard ledger as cutting occurs. Usually these are located between the guard
point or
at the rear edge of the sickles. Most are sheet metal and feature easy
adjustment
using a hammer or a simple single point threaded adjustment. By keeping the
hold-
downs separate from the guards fewer hold-downs than points may be used to
reduce the cost and number of adjustments required. Pointed guards have found
much favor in easier cutting conditions due to the ease of adjustment and
superior
performance.
Another form of guard is known as a stub guard which is formed in two
separate pieces including a base piece which carries the ledger surface and a
top
piece which extends over the ledger surface. The pieces are separate and
separately adjustable relative to the cutter bar so that the top piece can
apply
pressure onto the blade to press it onto the ledger surface. The pieces
terminate at a
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front edge which is just behind the front edge of the blade so that the front
edge of
the blade is presented to the crop.
In tough cutting, stub or no-clog guards have found the most favor.
Stub guards use a separate top and bottom guard pieces that spaced slightly
more
than one sickle blade thickness apart create a slot for the blade to operate
in. The
front edge of the blade protrudes slightly past the front tip of the two
guards. This
feature is what originally gave stub-guards their non-clogging self-cleaning
action. A
major improvement in stub guard technology was made when fully adjustable top
hold-down assemblies were introduced. These arrangements allowed the gap to be
io controlled much more precisely than previously so that the shearing
surface of the
blade was kept in close contact with the guard ledger surface. This
adjustability
allows the stub top piece to act as a much more effective hold-down than the
hold-
downs found on regular pointed guard systems.
The pointed guard has an advantage of presenting a point to the
.. incoming crop so that crop is effectively divided around it. This is
especially
advantageous when the sickle blade is at or near the end or start of each
stroke and
a front edge of each blade, which is typically a blunt front edge of a width
of the
order of 0.5 inch, is hidden partially or entirely within the guard slot.
Since the sickle
bar velocity is lowest at or near the end or start of each stroke this gives
the pointed
guard a considerable advantage over the stub guard for most crops.
The guards can be formed as single elements separately mounted on
the guard bar or as double or triple elements connected together side by side
for
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common mounting and common adjustment relative to the guard bar. There is no
reason why more elements might be included but this is not typical.
In some cases the arrangement is of the double sickle type where
each sickle bar is essentially half the length of the cutter bar and the
cutter bars
reciprocate in opposite phase to minimize vibrating mass and vibrations.
Usually the
sickle bars are timed so that they move in opposite directions so that
vibrations
induced into the cutter bar assembly are minimized.
The sickle knife cutting system has been widely accepted as the most
power efficient system due to the shearing action. However due to speed
restrictions of generally less than 5 to 8 mph ground speed, other systems
such as
rotating flail systems have come into use since these can be operated at much
higher ground speed of up to 14 mph while maintaining a high cutting
efficiency.
Such rotary systems have however much higher power usage, are limited in width
and provide crop handling difficulties for forming effective swaths for drying
of the
crop.
It remains therefore an ongoing and highly desirable objective to
construct a sickle knife system which can cut standing crop with sufficient
cutting
efficiency that the ground speed can be significantly increased. It is
believed that
the construction of a sickle cutting system which can operate at ground speeds
of
greater than 5 to 8 mph and up to 14 mph would enable the advantages of the
sickle
cutting action to take back the market currently being met by the flail
systems.
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Cutting crops such as soy beans where the bean pods can be located
closely adjacent the ground typically requires low ground speeds of around 4
to 5
mph to ensure that the crop is cut and fed into the combine harvester without
too
much loss of the pods. Pods can be lost if the cutting action causes some or
too
many of the lowest pods to be left at the stubble or broken up by the cutting
action. It
would be highly desirable to increase cutting speed above the typical range of
4 to 5
mph so as to increase this to or above 6 mph.
Cutting crops such as hay or forage crops such as alfalfa or grasses
typically allows higher ground speeds of up to 10 mph since the crop is more
io
resistant to a poor or inefficient cutting action. It would be highly
desirable to
increase cutting speed above the typical range of up to 10 mph so as to
increase
this to or above 12 or even 14 mph.
The term "sickle bar" as used herein is intended to refer generally to a
structure which supports all of the knife blades at the spaced positions along
its
length and is not intended to be limited to a single continuous element
extending
along the whole length of the structure. Thus the bar may be formed of
different
elements at different parts of the length and may include pieces below and
above
the blades.
SUMMARY OF THE INVENTION
According to the invention there is provided a sickle cutting apparatus
comprising:
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a plurality of stationary knife guards arranged to be mounted along a
cutter bar;
a sickle bar mounted in transversely extending position and arranged
to be driven for reciprocating movement relative to said knife guards;
the sickle bar having a plurality of knife blades mounted thereon for
movement therewith;
each of the knife blades having a cutting surface for passing across the
knife guards;
each of the knife blades having on first and second sides first and
second side cutting edges converging toward a forward tip of the blade;
each knife guard comprising a base portion arranged to be mounted on
the cutter bar and at least one guard finger mounted on the base portion so
that the
guard fingers are arranged to be mounted in a row along the cutter bar;
each guard finger having an upwardly facing ledger surface with
opposed side edges thereof arranged to provide first and second shearing edges
which cooperate with said side cutting edges of said knife blades;
and a plurality of hold-down members arranged to be mounted along
the cutter bar;
each hold-down member comprising a base mounting member
arranged to be attached to the cutter bar;
each hold-down member comprising at least one hold-down finger
thereon carried on the base mounting member arranged to be at positions spaced
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longitudinally of the cutter bar so as to be cantilevered forwardly from the
cutter bar
to a position of a front tip of each hold-down finger located at a spacing in
front of the
sickle bar above the ledger surface of a respective one of the guard fingers;
the guard fingers and hold down fingers thus forming cooperating
overlying pairs between which the blades pass in the cutting action;
the guard fingers having no portion elevated above the ledger surface
thereof in front of the tip of the blade;
wherein the guard fingers and blades have lengths from the cutter bar
arranged such that a forwardmost tip of the guard finger is forward of the tip
of the
.. blade.
Preferably also the guard fingers, blades and hold down fingers have
lengths from the cutter bar arranged such that a forwardmost tip of the hold
down
finger is rearward of the tip of the blade.
Preferably the tip of the guard finger is longer than the tip of the blade
by a distance up to 6.0 mm and preferably of the order of 3.0 mm.
Preferably the tip of the hold down finger is shorter than the tip of the
blade by a distance in the range 1.5 to 10.5 mm and preferably of the order of
5.0
mm.
The stubble which is cut by the knife blades and is longer than the
nominal cutting height is caused by the distance travelled over the ground
while crop
is in contact with and pushed by elements of the blades and guards as the
elements
move forward without cutting occurring. The elements include a trash bar of
the
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guard and a serrated edge of the blade where the crop is pushed forward by
engagement into a serration of the serrated edge.
It has been found, as described hereinafter, in relation to the
embodiments particularly described, that a significant increase in ground
speed
while maintaining an acceptable level of cutting efficiency as measured by the
average stubble length can be obtained by a combination of one or more of the
features where:
a) The distance between the center line of the guards which is
generally equal to the distance between the center line of the blades can be
equal to
the conventional length of 3.0 inches or may be reduced to a narrower width
typically
2.5 or 2.0 inch. This distance may be equal to the stroke length so that a
shorter
stroke length can allow a significant increase in reciprocation rate. However
the
stroke length may be a multiple of the center line distance. Even where the
stoke
length is not reduced so that the increase in reciprocation rate cannot be
achieved,
is .. the reduced center line distance has been shown to provide a significant
advantage.
b) the length of the cutting edge of each knife blade as measured
from a rearmost end of a cutting action to a forwardmost tip of the knife
blade is
increased from a conventional length to a length greater than 2.2 inches.
c) the width of the ledger surface of each guard at a position
thereon aligned with the rear end of the cutting edge of each knife blade is
increased
from a conventional length to a length greater than 1.0 inches or 1.2 or 1.5
inches.
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d) the front edge of the blade is formed with a pointed
portion
where the shape of an apex and side edges of the pointed portion are arranged
to
shed crop material engaging the point portion as the point portion is moved
forwardly
in the crop to one or other side of the point portion for cutting and to avoid
pushing
crop forwardly by the point portion.
This combination surprisingly provides a crop cutting efficiency which
is sufficiently high that the ground speed can be increased from the
conventional of
the order of 5 to 8 mph to 12 to 14 mph. This increase is significant and
significantly
alters the ability of the draper header to harvest forage crops such as
alfalfa at
greater than 10mph and up to 14 mph and to harvest soy beans at greater than
5mph and up to 6 or 7 mph.
The invention herein can be defined as or relate to the method of
cutting, the header for cutting, the guards and/or the knife blades. Thus each
of
these components of the invention includes aspects of the invention which
distinguish that component from the prior art as defined hereinafter.
A first improvement can therefore be obtained by providing a knife
blade which is narrower than conventional system so that typically the width
is equal
to approximately 2.0 inches center to center while providing a blade which has
a
length greater than conventional system so that the length from the trash bar
to the
tip is greater than 2.0 inches, greater than 2.2 inches or 2.5 inches and
typically of
the order of or greater than 2.75 inches.
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This can be further combined with an arrangement in which the width
of the guard at the trash bar is increased so that the width of each guard at
the rear
trash bar is equal to the maximum width which can be obtained while leaving a
space at the trash bar between the ledger surfaces of the order of 0.5 inch or
the
distance necessary to avoid pinching of crop stalks between the ledger
surfaces.
Typically each of the knife blades is generally triangular in shape so
that the side edges converge to a front edge at an angle of the order of 60
degrees
to the direction of reciprocating movement. The blade has a bottom cutting
surface
for passing across the ledger surface of the knife guards and an opposed or
upper
.. surface. The two converging side cutting edges are beveled from the upper
surface
to the bottom cutting surface to cooperate with the shearing edges of said
knife
guards. In addition the beveled side edges are typically serrated with grooves
running in a direction longitudinal to the reciprocating direction. In
order to
maximize the cutting action, the length of the cutting edge is substantially
the
maximum length extending from the trash bar at the rear to a position close to
the
front edge of the blade.
The fore-aft length of a blade has traditionally been in the order of 45
mm (1.75 in) from the front of the trash bar, that is the rearmost cutting
location or
the rear of the cutting action, to the tip of the section, or 55 mm (2.2 in)
from the front
edge of the knife back to the tip of the section. Traditionally this dimension
is usually
similar to the length of the cutting edge.
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In this new arrangement, the fore-aft length of the blade is increased
substantially. Thus the length of cutting edge of each sickle blade from a
rearmost
end of the cutting action at the trash bar, or to the rear of the shearing
action on the
ledger surfaces, to a front edge of the blade in the present invention is
greater than
1.75 inches. This can lie in the range 2.2 to 3.0 inches.
The term "trash bar" as used herein typically is defined by a specific
transverse bar interconnecting to the ledger surfaces of the lower guards but
does
not require the provision of a specific bar member extending across the blades
but
merely relates to the position of that component of the system where the crop
is
halted as it moves rearwardly between the guard fingers. Thus at some point
the
crop is halted so that it remains in the position where it can be engaged by
the side
edges of the blades and can be cut in the shearing action relative to the side
edges
of the ledger surface. This element which halts the crop movement is called
herein
the "trash bar".
This also reduces the angle of inward inclination of the cutting edge
from the typical 30 degrees to an angle less than 20 degrees and typically of
the
order of 15 degrees and in the range 15 to 30 degrees.
Thus in one example the blade has a width of 2.0 or 3.0 inches at the
base and a length from the front of the trash bar to the tip of 2.5 inches.
It is common practice for sickle sections, of the current type having
beveled and serrated side edges, to have a front edge in the order of 15 mm
(0.6
inches) wide. When used with a pointed guard, this is not as much of a problem
as
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this edge is sometimes in the shadow of the guard. However, even with pointed
guards and certainly when used with stub guards, the wide tip has the
potential for
running down crop or pushing the crop forwardly with the forward motion of the
cutter bar, thus leaving more long uncut stems greater in length than the
nominal
minimum value above thus significantly increasing the average length with is
the
measure herein of cutting efficiency. In present invention the blade is
designed with
a pointed tip, thus eliminating the problem when used with stub guards.
In some crop conditions e.g. forage with a mat of wet leaves near the
ground, pointed guards will tend to plug due to "mouse nesting" on the guard
point. It
is therefore important that a cutting system works well with stub guards.
The intention is therefore to provide a sickle blade which is as pointed
as reasonably practical. A sharp point is difficult to obtain so that
typically the front
edge is smoothly curved with a radius of curvature less than 0.5 inches thus
defining
a front apex which is sufficiently narrow to shed crop stalks to each side,
That is,
each knife blade has a front point portion in front of the cutting edges which
has side
edges converging to front apex where the apex and the side edges are shaped
and
arranged such that crop material engaging the point portion, as the point
portion is
moved forwardly in the crop, is shed to one or other side of the point portion
for
cutting and is not pushed forwardly by the point portion. In the present
arrangement
the front apex is not a point as this can be damaged but is a curved front
edge of a
radius of curvature less than 0.5 inches and preferably less than 0.25 inches.
From
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this curvature the sides of the pointed portion diverge rearwardly at an angle
approximately equal to or slightly greater than the angle of the cutting
edges.
In a blade which has a center to center spacing of the order of 2.0
inches and a length from apex to trash bar greater than 2.0 inches, the angle
of the
side edges of the blade is less than 20 degrees and can be as low as 15
degrees.
The angle of the side edges of the front point portion can be be greater
and is typically in the range 30 to 45 degrees and preferably of the order of
35
degrees.
This curvature at the apex and the angle of divergence from the
curved apex acts to shed the crop to the sides and to avoid trapping and
pushing the
crop forwardly.
While this is the optimum arrangement, a practical construction may
have a straight line across the apex with a transverse width which is much
less than
the conventional 0.6 inches and is typically less than 0.25 inches.
Thus each knife blade has a front point portion in front of the beveled
and serrated side cutting edges which front point portion has side edges
converging
to front apex, where the apex and the side edges of the front point portion
are
shaped and arranged such that crop material engaging the front point portion,
as the
point portion is moved forwardly in the crop, is shed to one or other side of
the front
point portion for cutting by the side cutting edges and is not pushed
forwardly by the
front point portion.
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Preferably the beveled side sedges are serrated in a direction at right
angles to a forward direction.
Preferably the pointed portion has a thickness at the apex equal to that
of the blade.
Preferably the beveled edges are reduced in width at as they approach
the pointed portion leaving a strip of the upper surface between the beveled
edges
having thickness equal to that of the blade with side edges of the strip being
parallel
to the center line of the blade.
Preferably at this strip the beveled edges become narrower as the
3.0 beveled edge approaches the front pointed portion of the blade.
Preferably the beveled edges and the serrations therein terminate at a
position spaced from the apex of the pointed portion such that the front
pointed
portion forms an arrow-head shape in front of a forwardmost one of the
serrations
with the width of the front pointed portion being substantially equal to the
width of the
side edges at the forwardmost one of the serrations.
Preferably a center line spacing between each knife blade and the next
is less than 3.0 inches, preferably less than 2.5 inches and more preferably
of the
order of or equal to 2.0 inches. Thus the center line spacing can be equal to
the
conventional value of 3.0 inches.
Preferably a length of each knife blade from the trash bar to a
forwardmost tip of the knife blade is greater than 2.0 inches, preferably
greater than
2.2 or 2.5 inches and more preferably greater than 2.75 inches.
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Preferably the front point portion has side edges which are not
sharpened.
Preferably the radius of curvature of the front pointed portion at the
apex is less than 0.5 inch and more preferably less than 0.25 inch.
The characteristics of the blade defined above, where it is narrower
than conventional, 2.0 inches as opposed to 3.0 inches, and significantly
longer,
greater than 2.2 inches or 2.5 to 2.75 inches as opposed to 2.2 inches places
considerable limitations on the shape and arrangement of the beveled and
serrated
edges.
In order to form the pointed portion at the front edge in front of the
beveled edges, the beveled edges are reduced in width as they approach the
front
edge leaving a strip of the upper surface between the beveled edges with side
edges of the strip parallel to a center line of the blade. Thus at this strip
the beveled
edge becomes narrower and the grooves in the edge get shorter as the beveled
edge approaches the front apex of the blade. The beveled edges and the
serrations
therein terminate at a position spaced from the front apex to define an arrow-
head
shaped pointed portion in front of the beveled edges which imparts sufficient
strength to the construction to allow the formation of the serrations. The
thickness
of the blade through the main body of the blade excluding the beveled edges is
constant so that the pointed portion and the apex have the same thickness as
the
rest of the main body of the blade and the bevel which reduces the thickness
does
not extend to the apex.
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The cutting efficiency and therefore stubble length are also affected by
the width of the cutting edge of the knife guard. Generally, the width at the
rear of
the cutting edge on the guard is in the order of 25 mm (1.0 in). In the
arrangement
of the present invention that width is substantially increased. Thus the width
of
each guard at a position thereon aligned with the rear end of the cutting edge
of
each blade is greater than 1.0 inches or 1.2 inches or 1.5 inches. The maximum
width of the guard is slightly less than the center to center spacing of the
blades
since it is necessary to leave a gap between the guards at the back to prevent
pinching the crop and to allow the crop to reach the back for the rearmost
cutting
action. Thus with a blade center to center spacing of 2.0 inches the width of
the
guard is slightly less than that of the width of the blade or roughly 1.9
inches. Thus
with a blade of this width, the width of the guards can be as much as 1.9
inches and
preferably lies in the range 1.2 to 1.9 inches. However where the blade is
greater
than 2.0 inches in width, the guard can have a width which is between 0.5 and
0.1
inches less than the width of the blade.
Thus the arrangement provided herein provides a center line spacing
between each guard finger and the next which is in some cases less than 3.0
inches
and more preferably 2.0 inch where a width of each guard at the rear trash bar
is
greater than 1.5 inches and preferably 1.75 inches.
Thus a width of each guard at the rear trash bar is equal to the
maximum width which can be obtained while leaving a space at the trash bar
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between the ledger surfaces of the order of 0.5 inch or the distance necessary
to
avoid pinching of crop stalks between the ledger surfaces.
Preferably the stroke length is equal to the center line spacing between
the knife blades.
Preferably, at the position in the stroke where the center line of the
knife blades is aligned with the center line of the guard fingers, the side
cutting
edges of the knife blades substantially directly overlie the side edges of the
ledger
surface.
Preferably each knife blade has a front point portion in front of the side
cutting edges which front point portion has side edges converging to front
apex,
where the apex and the side edges of the front point portion are shaped and
arranged such that crop material engaging the front point portion, as the
point
portion is moved forwardly in the crop, is shed to one or other side of the
front point
portion for cutting by the side cutting edges and is not pushed forwardly by
the front
is point portion.
Of course ground speed can be increased if the operator has no
regard for cutting effectiveness and the quality of the cut crop. This is of
course
unacceptable.
One measure of cutting effectiveness is that of the length of stubble
which remains on the ground. If the cutting blades run at a nominal height
from the
ground then they will theoretically cut all crop to a nominal length equal to
the height
of the blade from the ground. However this does not occur as the sickle knife
moves
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forwardly since not all crop is cut immediately as it enters the cutting
system. As
some cutting is delayed and the crop pushed forwardly by engagement with
elements of the cutting system to bend over from the normal upstanding
position,
then some stubble will have a length exceeding the nominal length and this
length
difference will increase as the ground speed increases. Thus cutting
effectiveness
can be measured by detecting and measuring the average length difference of
stubble which exceeds this nominal length.
An acceptable effectiveness is defined where the average stubble
length difference, that is the average length beyond the minimum or nominal
length
defined by the distance of the blades from the ground, is less than 1.0
inches, as
measured at a set speed of 10 mph. Thus for example where the nominal height
is
a typical 1.5 inches, an acceptable effectiveness is where a measured average
length is no greater than 2.5 inches.
Of course machines can run at different speeds and there is no
intention herein to limit the speed to a particular value. However as the
stubble
length is of course speed dependent, it is necessary, in order to analyze the
system,
to set a predetermined value at which the stubble length is measured.
Of course in a practical situation there may be failures in proper cutting
action leaving some crop stalks greater than the allowed length difference
defined
above. However discarding such discernible failures in the cutting action
which are
due to cutting errors and are not a measure of the actual efficiency of the
proper
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cutting, a proper efficiency is defined by the average stubble length as set
forth
above.
Thus the best measure of cutting effectiveness is the stubble length
that is left after cutting. The requirement however will vary depending on the
crop.
For example for a wheat crop, it will not be critical that a short stubble
length be
maintained, as the heads are generally high on the plant.
In the case of hay (alfalfa) it will be important that a fairly short stubble
length is maintained so that a significant quantity of crop is not left in the
field. A
typical acceptable total average stubble length in this case would be in the
area of
2.75 inches (that is 1.25 inches longer than the nominal minimum length). Thus
the
ground speed can typically exceed the 10 mph value set above for the above
analysis and may be as high as or higher than 14 mph.
In the case of soybeans, the acceptable average stubble length
depends on the general height of the lowest bean pod on the plants. The
acceptable
average stubble length thus varies from about 2 to 2.5 inches or 0.5 to 1.0
inches
greater than the nominal value. In this case a speed of less than 10 mph is
likely to
be desirable.
The guard fingers, knife blades and the trash bar are arranged so as to
provide a cutting action on the crop in which:
in a first cutting stroke, each knife blade moves across from one
guard finger to the next in a first direction so as to cut crop located on
said first side
of the knife blade between the first cutting edge of the knife blade and the
next guard
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finger by the shearing action while leaving uncut crop located on the second
side of
the knife blade;
and, in a second cutting stroke, each knife blade moves across
from the next guard finger to said one guard finger in a second direction so
as to cut
crop located on the second side of the knife blade between the second cutting
edge
of the knife blade and said one guard finger by the shearing action, including
said
uncut crop, while leaving uncut crop located on the second side of the knife
blade.
While this crop remains upstanding before it is cut, the stubble length
remains at the nominal value. However as soon as the crop is pushed forwardly
by
a non-cutting surface or a cutting surface which is not in a cutting action at
that
position in the stroke, it begins to bend over and its length when it is cut
is increased
from the nominal value by the distance the crop is bent forwardly.
The guard fingers, knife blades and the trash bar are shaped and
arranged therefore to provide a percentage cutting inefficiency of less than
35%,
30% or 25%, at the above set speed of 10 mph and at a sickle stroke rate set
at a
value which provides inertia values equal to those obtained by a three inch
stroke at
750 rpm,
where percentage cutting inefficiency is calculated as follows:
within a rectangular area defined by the length of the knife
stroke and the ground distance travelled during one knife cycle, the sum of
any
areas of crop in which the crop remains uncut until it reaches an element of
the
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cutting system by which the crop is pushed forward, without cutting, by
contact with
the element as the element moves forward;
divided by:
the rectangular area defined by the length of the knife stroke
and the ground distance travelled during one knife cycle.
Thus in a first cutting stroke, there is an area of crop located on the
second side of each knife blade in which the crop is gathered by contact with
the
guard fingers and trash bar as the guard fingers and trash bar move forward
while
the knife blade is cutting on said first side of said knife blade.
Symmetrically in a
second cutting stroke, there is an area of crop located on the first side of
each knife
blade that is gathered by contact with the guard fingers and trash bar as the
guard
fingers and trash bar move forward while the knife blade is cutting on said
second
side of said knife blade.
The elements which can engage and push the crop while not cutting
the crop as the blade moves away from those elements include the trash bar and
the
serrated edge of the blade on the understanding that crop cannot slide along
the
serrated blade but instead will remain at a particular serration and be pushed
forward by the blade at that location until the return stroke cuts the crop.
There is in many prior art arrangements an area that is generated by
any crop which is pushed forward by contact with a front edge of the knife
blade. In
the present invention the blade is of a shape to shed the crop thus reducing
this
significant inefficiency.
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The definition of inefficiency can also be applied at different ground
speeds wherein the percentage cutting inefficiency can calculated at 6 mph and
at a
sickle stroke rate set at a value which provides inertia values equal to those
obtained
by a three inch stroke at 600 rpm, is less than 30%; or the percentage cutting
inefficiency can be calculated at 10 mph and at a sickle stroke rate set at a
value
which provides inertia values equal to those obtained by a three inch stroke
at
750 rpm, is less than 35%; or the percentage cutting inefficiency can be
calculated at
14 mph and at a sickle stroke rate set at a value which provides inertia
values equal
to those obtained by a three inch stroke at 900rpm, is less than 40%.
10. The
reason for identifying the theoretical calculated efficiency at three
different speeds of 6, 10 and 14 mph is that different machines can be
designed and
arranged to travel at different speeds.
Thus for example a 40 foot header used as a straight cut header for a
combine can have a sickle knife length of 40 feet and can be designed to
travel in
the range 2 to 8 mph so that using a pre-set speed of 6 mph and a stroke rate
of
600rpm falls reasonably in the range of a machine of this type.
The present invention sets out that, at the pre-set speed and pre-set
stroke rate, the shape and arrangement of the cutting system is such that it
obtains
the stated inefficiency. Of course, at different speeds and stroke rates, the
same
cutting system will have different inefficiencies, but in order to determine
whether a
cutting system provides the inefficiency of the present invention, pre-set
parameters
must be determined to allow the calculation to be carried out.
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Thus as another example, at 14 mph the machine concerned can be of
the type for cutting hay or forage crops and will have a header of for example
20 feet
in width with two 10 foot sickle knives.
At 10 mph the machine has intermediate characteristics. The pre-set
characteristics used therefore are set forth as alternative to determine the
actual
theoretical calculated inefficiency of the cutting system of a machine and the
calculation can be carried out at those pre-set characteristics selected from
the
above different examples which best match the range of operation of the
machine
concerned.
1.0 As
defined in the figures hereinafter, the sickle stroke rate for a 4.0
inch stroke, which provides inertia values equal to those obtained by a 3.0
inch
stroke at 750 rpm, is 650rpm and the sickle stroke rate for a 2.0 inch stroke,
which
provides inertia values equal to those obtained by a 3.0 inch stroke at 750
rpm, is
918rpm.
The pre-set parameters for the inefficiency calculation are set out in
table 23 hereinafter.
In order to achieve the above decrease in cutting inefficiency, the
following characteristics are preferably to be selected, although other
characteristics
may when analyzed provide the same level of inefficiency:
---a center line spacing between each knife blade and the next which is
less than 3.0 inches and preferably of the order of 2.0 inches.
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--- a length of each knife blade from the trash bar to a forwardmost tip
of the knife blade which is greater than 2.0 inches and preferably of the
order of 2.75
inches.
--- a width of each guard at the rear trash bar which is greater than 1.0
inches and preferably, for a guard spacing center to center of 2.0 inches of
the order
of 1.75 inches. That is the width of each guard at the rear trash bar is equal
to the
maximum width which can be obtained while leaving a space at the trash bar
between the ledger surfaces of the order of 0.5 inch or the distance necessary
to
avoid pinching of crop stalks between the ledger surfaces.
Preferably the stroke length is equal to the center line spacing between
the knife blades.
Preferably at the position in the stroke where the center line of the
knife blades is aligned with the center line of the guard fingers, the side
cutting
edges of the knife blades substantially directly overlie the side edges of the
ledger
surface.
Preferably each knife blade has a front point portion in front of the side
cutting edges which front point portion has side edges converging to front
apex,
where the apex and the side edges of the front point portion are shaped and
arranged such that crop material engaging the front point portion, as the
point
portion is moved forwardly in the crop, is shed to one or other side of the
front point
portion for cutting by the side cutting edges and is not pushed forwardly by
the front
point portion.
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=
Preferably the front point portion has side edges which are not
sharpened.
While much of the description herein is directed to a narrower cutting
system using blades of 2 inch width, the same cutting action and operation of
the
blades can be obtained with blades which have a spacing from tip to tip of 3
inches.
Preferably each blade with a base portion and only two cutting edges
is a separate component from each of the other blades so that the side edges
of
each blade lie immediately adjacent the side edges of the next adjacent
blades.
However blades can be formed in pairs connected to the same base
Preferably the blade has only a single cut out opening luing
symmetrically on the center line and converging to an apex directed toward the
apes
of the blade. However more than one cu out opening can be provided with
different
shapes.
Preferably the cut out opening has a rear edge parallel to a rear edge
of the blade, two side edges substantially parallel at right angles to the
rear edge
and two converging edges extending from the side edges to a forward apex.
Preferably the length of each blade from the transverse line defining
the rearmost cutting action to the forwardmost tip of the knife blade is
greater than
2.5 inches. A maximum of less than 2.9 inches is preferred.
BRIEF DESCRIPTION OF THE DRAWINGS
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Figure 1 is a top plan view of a part of header showing a portion of the
sickle knife according to a first embodiment of the present invention using a
stub
guard.
Figure 2 is a cross-sectional view along the lines 2-2 of Figure 1.
Figure 2A is a side elevational view of a sickle apparatus showing the
engagement of the front edge of the knife and the engagement of the trash bar
with
the crop which leads to cutting inefficiencies leading to maximum stubble
length
increases.
Figure 3 is top plan view of a knife blade for use in the sickle knife of
Figure 1.
Figure 4 is a side elevational view along of the knife blade of Figure 3.
Figure 5 is top plan view of one knife blade of Figure 3 on an enlarged
scale showing the angles of the side edges for different length blades.
Figure 6 is top plan view of a knife blade of the type of Figure 3
showing a different width blade.
Figure 7 is a top plan view of a part of header showing a blade of a
sickle knife according to a second embodiment of the present invention using a
pointed guard.
Figure 8 is a cross-sectional view along the lines 8-8 of Figure 7.
Figure 9 is top plan view of another embodiment of cutting system
using a 3 inch spacing of the blades and using stub guards.
Figure 10 is a cross sectional view along the lines 10-10 of Figure 9.
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Figure 11 is a detail of the cross-sectional view of Figure 10 showing
the tips of the bottom guard finger, blade and hold down finger.
Figure 12 is top plan view of another embodiment of cutting system
using a 3 inch spacing of the blades and using pointed guards.
Figure 13 is a cross sectional view along the lines 13-13 of Figure 12.
Figure 14 is a detail 14 of the cross-sectional view of Figure 13
showing the shape of the tang portion.
Figure 15 is a detail 15 of the plan view of Figure 12 showing the
shape of the tang portion.
Figure 16 is a top plan view of blade of the embodiments of Figures 9
and 12.
DETAILED DESCRIPTION
In Figures 1 and 2 is shown a first embodiment of a crop cutting device
generally indicated at 10. Only a part of the complete machine is shown since
the
remainder of the machine may vary widely depending upon requirements and since
the construction is of course well known to a person skilled in the art. In
this
embodiment as shown, there is a frame generally indicated at 11 which forms
only
one part of the total frame structure that is the part of the frame that is
relevant to the
present invention.
The cutting device 10 further includes a cutter bar 12 attached to the
frame structure 11. Thus the frame structure 11 in the part as shown comprises
a
guard bar 13 to which is attached a plurality of knife guards 14. The guard
bar 13 is
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attached to the frame structure which supports the guard bar in fixed position
across
the front edge of the frame for a cutting action of the crop cutting device on
the
standing crop.
Each knife guard 14 includes one or more guard fingers 14A so that
guards can be arranged with a single finger, pair of fingers or triples. As
shown the
guard bar forms a triple guard construction with three fingers where a series
of such
guards are mounted on the guard bar 13 at spaced positions along the length of
the
guard bar. In the embodiment as shown, only one of the guards is shown but it
will
be appreciated that there are additional guards as required to provide a crop
cutting
device of a required width.
The knife guards shown in Figures 1 and 2 are basically of a
conventional construction of a stub guard in that each guard finger 14A
includes a
lower portion 15 and an upper portion 16. These two portions are mounted on
the
guard bar 13 by a mounting arrangement 17 including bolts 18. The mounting
arrangement thus attaches a rear end 19 of the lower portion 15 rigidly on the
underside of the bar 13 so that the fingers of the guard project forwardly
from the bar
to a front nose 20. Similarly the upper portion 16 is mounted on the guard bar
13 by
an adjustment plate 21 attached onto the same bolts 18. Upper portion 16 has
fingers which extend forwardly to a nose 22.
In the embodiment shown the guards are stub guards so that the
noses 20, 22 of the upper and lower portions substantially overlie one another
and
confine between them the blades 23 of the sickle bar or knife back 24.
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Each pair of guards thus includes two guard elements each defined by
an upper portion and a lower portion and the guard elements are shown in FIG.
1 at
15 and 16. A front crop guide bar or trash bar 28 is also provided. Between
the
mounting bar 21 and the front guide bar 28 is provided a channel 25 within
which the
sickle bar or knife back 24 is mounted for reciprocating movement.
The trash bar may form a continuous bar member extending along the
lower guard portion 15 in front of the bar 24 to prevent any crop reaching
that area.
However the trash bar may be formed by any part of the system which prevents
the
crop from moving rearwardly beyond the rear end of the cutting edges of the
blades.
There may be a single sickle bar driven from one end or in some cases
there are two sickle bars driven from opposite ends and meeting in the middle.
The
sickle bar or bars are driven by the reciprocating drive motor (not shown but
conventional) such that the bar reciprocates back and forth.
In some cases the bar reciprocates by a distance Si equal to the
space between the nose of one guards 15, 16 and that of the next along the
guard
bar 13 so that the blades reciprocate from a position with the center line of
the knife
aligned with the center line of the first guard to a position aligned with the
next and
back to the first. In other cases, the reciprocation stroke may be as shown at
S2 a
multiple of, typically double, the distance between the guards so that the
knife
moves from a first guard finger across a second to a third and back to the
first. This
arrangement reduces the available reciprocation rate due to increased
acceleration
forces but reduces the number of reversals.
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Each sickle bar comprises the support bar member 24 and the plurality
of blades indicated at 23. As shown the blades are formed in pairs mounted on
a
common base as shown in Figure 3, but individual blades may be provided or in
some cases the blades may have more than two on the same base.
Each of the blades forms a generally triangular-shaped member which
has a rear end or base 23A bolted to the bar and converges from the rear end
to a
front end 23B. Each of the blades has a top surface 23D and a bottom surface
23E.
Each of the blades has a side edge 23F and a second side edge 23G. The sides
edges are beveled from the top surface down to the bottom surface 23E so that
a
sharp edge is formed at the bottom surface at each of the side edges. The
blades
are also serrated at each cutting edge with grooves 23L, 23M extending
parallel to
the bars 24 that is at right angles to a center line 23H.
The top member 16 acts to hold the blades downwardly into
engagement with the top ledger surface 15A of the bottom portion 15. The
bottom
portion 15 has two side edges of the ledger surface 15A as best shown in FIG.
2
with those side edges 15B and 15C acting as side edges of the ledger surface
15A.
Thus the cutting action of the blades occurs between the ledger 15A and the
bottom
surface 23E of the blade as the blade reciprocates from its position at one of
the
guards to its position at the next adjacent one of the guards. In this cutting
action,
therefore, the side edge of the blade moves across the space between the
guards
and enters onto the ledger surface of the next guard in a cutting action
between the
bottom surface of the blade and the top surface of the guard which are
immediately
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adjacent and generally in contact or at least closely adjacent to provide a
shearing
action on the crop.
In these guards, the upper portion 16 acts merely as a hold down
member contacting the upper surface of each of the blades so as to prevent it
from
moving away from the ledger surface 15A by applying pressure to that upper
surface
23D of the blade and holding the blade in contact with or closely adjacent the
ledger
surface 15A of the bottom portion where the cutting action occurs. The upper
portion
16 therefore as shown in Figure 1 has side surfaces 16B and 16C of the bottom
surface 16A which is narrower than the ledger surface 15A of the bottom
portion 15.
The mounting and adjustment arrangements for the bottom portion 15
and the upper portion 16 can vary in accordance with a number of different
designs
readily available to a person skilled in the art. It suffice to say that the
hold down
portion 16 is adjustable so that the gap between the bottom surface of the
hold down
portion and the ledger surface of the bottom portion 15 can be adjusted to
allow the
sliding action of the blades while holding the blades in the required
position.
The disclosures of the following documents of the present Applicants
may be referred to for details of the construction not provided herein. These
show
various conventional details of the sickle knife system which can be used in
the
arrangement herein but are not described as they are known to persons skilled
in
the art.
US Patent 7,328,565 (Snider) issued February 12 2008;
U.S. Patent 4,894,979 (Lohrentz) issued Jan. 23, 1990
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U.S. Patent 4,909,026 (Molzahn) issued Mar. 20, 1990.
U.S. Patent 6,962,040 (Talbot) issued Nov 8, 2005.
US Application 13/680,557 filed November 19 2012 based on a
Provisional application 61/577,427 filed December 19 2011 (Talbot) relating to
an
adjustable hold down.
In Figure 1, a drive for knife bar 24 is indicated schematically at 24A.
This can comprise any suitable drive system known to persons skilled in this
art of a
= type which can generate a stroke Si of 2 inches at a drive rate of
typically 918 rpm.
The system can also be arranged in an alternative embodiment to drive the
stroke
S2 of 4 inches in which case the reciprocation rate may be lower. The drive
system
24A includes an input from a ground speed indicator 24B which allows automatic
adjusting of the stroke rate of the drive system 24A in dependence on ground
speed.
As the system herein provides a cutting efficiency which is higher than that
of
previous designs and suitable for cutting at speeds as much as 14 mph, it is
possible
when running at lower ground speeds such as less than 10 mph to reduce the
drive
rate of the knife since the maximum cutting effect is not required at those
lower
ground speeds. Thus the system can be arranged to automatically control the
knife
speed to a lower fixed value when the ground speed is less than a
predetermined
set value or to provide a proportional control of the drive speed.
The knife blade 23 is narrower than conventional system so that
typically the width W is equal to the stroke length which is approximately 2.0
inches
center C to center C while providing a blade which has a length L greater than
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conventional system so that the length from the trash bar 28 to the tip 23K is
greater
than 2.0 inches and typically of the order of or greater than 2.75 inches.
This can be further combined with an arrangement in which the width
W1 of the guard ledger surface at the trash bar 28 is increased so that the
width W1
of each guard at the rear trash bar is equal to the maximum width which can be
obtained while leaving a space S at the trash bar between the ledger surfaces
of the
order of 0.5 inch or the distance necessary to avoid pinching of crop stalks
between
the ledger surfaces.
Typically each of the knife blades is generally triangular in shape with
1.0 straight side edges 23F, 23G. However other shapes of the side
edges 23F, 23G in
plan such as convex or concave can be used. Thus the side edges 23F, 23G
converge to the front apex 23K at an angle of the order of 60 degrees to the
direction of reciprocating movement. The two converging side cutting edges
23F,
23G are beveled from the upper surface 230 to the bottom cutting surface 23E
to
cooperate with the shearing edges of the knife guards. In addition the beveled
side
edges are serrated with grooves 23L, 23M running in a direction longitudinal
to the
reciprocating direction. In order to maximize the cutting action, the length
of the
cutting edge is substantially the maximum length extending from the trash bar
28 at
the rear to a position close to the front apex 23K of the blade.
In this new arrangement, the conventional fore-aft length of the blade
is increased substantially. Thus the length of cutting edge of each sickle
blade from
a rearmost end of the cutting action at the trash bar 28, or to the rear of
the shearing
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action on the ledger surfaces 15A, to the front apex 23K of the blade in the
present
invention is greater than 1.75 inches. This can lie in the range 2.2 to 3.0
inches.
The cutting efficiency and therefore stubble length are also affected by
the width of the cutting edge of the knife guard. In the arrangement of the
present
invention that width is substantially increased. Thus the width W1 of each
guard at
the trash bar 28 is greater than 1.0 inches. The maximum width of the guard is
slightly less than the center to center spacing of the blades since it is
necessary to
leave the gap S between the guards at the back to prevent pinching the crop
and to
allow the crop to reach the back for the rearmost cutting action. Thus with a
blade
center to center spacing of 2.0 inches the width W1 of the guard is slightly
less than
that of the width of the blade or roughly 1.9 inches. Thus with a blade of
this width,
the width of the guards can be as much as 1.9 inches and preferably lies in
the
range 1.2 to 1.9 inches. However where the blade is greater than 2.0 inches in
width, the guard has a width which is between 0.5 and 0.1 inches less than the
width
of the blade.
At the position in the stroke shown in Figure 1 where the center line C
of the knife blades is aligned with the center line Cl of the guard fingers,
the side
cutting edges of the knife blades 23F, 23G substantially directly overlie the
side
edges 15B, 150 of the ledger surface 15A.
Each knife blade has a front point portion 23X in front of the side
cutting edges 23F, 23G which front point portion has side edges 23N, 23P
converging to the front apex 23K, where the apex and the side edges of the
front
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point portion 23X are shaped and arranged such that crop material engaging the
front point portion, as the point portion is moved forwardly in the crop, is
shed to one
or other side of the front point portion for cutting by the side cutting edges
and is not
pushed forwardly by the front point portion 23X.
As shown in Figures 3, 4 and 5, the arrow head shaped front point
portion 23X has side edges 23N, 23P which are not sharpened. The angle of the
bevel of the sides 23F and 23G may extend partly into the side edges 23N and
23P
but the side edges 23N and 23P are not beveled to the bottom surface 23E so
that
they are not sharp. Also the last serration 23Y of the bevel edges 23F and 23G
is
located at the bottom of the portion 23X so that the side edges 23N and 23P
are not
serrated. The pointed portion 23X has a thickness at the apex 23K equal to
that of
the blade so that as shown in Figure 4B, the thickness along the center line
remains
constant right up to the apex 23K. The arrangement is designed so that the
front
portion 23X is as thick as possible over its full extent consistent with the
requirement
is to
machine the blade to form the beveled and serrated edges 23F, 23G. Thus the
beveled side edges 23N and 23P are reduced in width in plan view at as they
approach the pointed portion 23X leaving a strip 23R of the upper surface
between
the beveled edges having thickness equal to that of the blade with side edges
23Q
of the strip being parallel to the center line 23H of the blade. Thus, at this
strip 23R,
the beveled side edges 23N and 23P become narrower as the beveled side edges
23N and 23P approach the front pointed portion 23X of the blade.
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The beveled side edges 23N and 23P and the serrations 23L therein
terminate at the position 23Y spaced from the apex 23K of the pointed portion
23X
such that the front pointed portion 23X forms an arrow-head shape in front of
a
forwardmost one 23Y of the serrations with the width of the front pointed
portion 23X
being substantially equal to the width of the side edges 23N and 23P at the
forwardmost one 23Y of the serrations.
As shown in Figures 3 and 4, a center line spacing CLS between each
knife blade and the next is less than the conventional value of 3.0 inches and
preferably of the order of or equal to 2.0 inches. It will be appreciated that
a
measurement of center to center spacing which is equal to an integral number
of
inches is preferred for engineering reasons but in theory it is not essential
to have an
integral number and in some cases the spacing can be in millimeters. In
practice, a
spacing in the range 2.5 to 1.5 inches is suitable. In Figure 6 (not to scale)
a wider
spacing of 2.5 inches is shown. In Figure 5 the angles of different lengths of
blade
are shown where a blade having a length of at least 2.5 inches from the trash
bar is
shown having an angle A2 of the side edges and a shorter blade having a length
of
the order of 2.0 inches from the rash bar has angles A3. In each case the
angles of
the side edges 23N and 23P is slightly greater than that of the cutting edges.
As shown in Figures 3 and 4, a length L along the center line 23H of
each knife blade from the trash bar that is the rearmost end 23T of the
cutting edge
23F to the forwardmost tip 23K of the knife blade is substantially equal to or
greater
than 2.75 inches. Improvement in cutting efficiency is obtained by increasing
the
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length of the blade so that the selection of a value of at least 2.75 inches
is preferred
which provides the improved cutting action while avoiding a blade which has a
length greater than can be manufactured to remain stiff and straight in the
cutting
action without danger of bending. Improvement can be obtained at any value
greater than conventional blades so that any value greater than 2.0 inches is
within
the invention herein. A length greater than 2.5 inches will provide a
significant
improvement.
In order to provide shedding of crop at the apex, the radius of
curvature of the front pointed portion at the apex is less than 0.5 inch and
preferably
less than 0.25 inches. However a blunt front edge is possible provided it
is
sufficiently narrow and a value of less than 0.25 inch or more preferably less
than
0.125 inch is possible.
The above geometry provides a construction in which the side edges
of the blade are arranged relative to a center line of the blade at an angle
less than
30 degrees and preferably less than 25 degrees.
Similarly the side edges of the front portion, which are typically but not
necessarily at the same angle as the side edges of the blade, are arranged
relative
to a center line of the blade at an angle less than 30 degrees and preferably
less
than 25 degrees. In practice this angle is preferably of the order of 20
degrees.
Thus the preferred construction provides a center line spacing between
each knife blade and the next is of the order of or equal to 2.0 inches, the
radius of
curvature of the front pointed portion at the apex is less than 0.25 inch and
the side
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edges of the front portion are arranged relative to a center line of the blade
at an
angle of the order of 20 degrees.
As shown in Figure 1, the width between the centers of the guards is
indicated at D. This can be the same as the length of the cutting stroke so
that the
blades move from a position aligned with the center line of one guard finger
to that of
the next. However in some embodiments the stroke may be a multiple of the
distance D, typically twice, so that the blades move from the first guard
finger to the
third crossing the second. The reversal of the reciprocating action at the
guard
center line ensure that the blades are stationary and therefore carrying out
no cutting
when they are overlying the guard and not at an intermediate location. The
increase
of the stroke length to a multiple of the finger reduces the number of times
the
blades are stationary but requires a reduced stroke rate due to the increased
forces
on the drives system.
This distance D is less than 3.0 inches and is more preferably of the
is order of 2.0 inches. Typically the stroke can lie in the range 1.5 to
2.5 inches since
this provides a stroke length which allows an increase in the cutting
reciprocation
rate of the sickle bar by a percentage of the order of 22%. This allows a
typical rate
of 600 cycles per minute, suitable for a 40 ft sickle bar, to be increased a
rate
greater than 750. For shorter bars this rate can be greater than 900. The
length of
the stroke and the rate are determined by the selected geometry of the drive
system.
Typically each of the knife blades 23, as shown in Figure 2, is
generally triangular in shape. In the example shown, the blade 23 forms a
double
CA 2976845 2017-08-21
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blade connected by a base 23A. The base has holes 23J for mounting on the
blade
drive bar 24. The blade 23 has two side edges 23F, 23G which converge at an
angle A to the direction of reciprocating movement. At the front of the blade
is
provided a front apex 23K of a front arrow head shaped portion 23X.
The blade has a bottom cutting surface 23E for passing across the
ledger surface 15A of the bottom knife guards 15 and an opposed or upper
surface
23D. The two converging side cutting edges 23F, 23G are beveled from the upper
surface 23D to the bottom cutting surface 23E to cooperate with the shearing
edges
of the knife guards. In addition the beveled side edges 23F, 23G are typically
io serrated with grooves 23L, 23M running in a direction longitudinal to the
reciprocating direction. In
order to maximize the cutting action, the length of the
cutting edge is substantially the maximum length extending from the trash bar
28 or
the rear edge 23T at the rear to a position at the front edge or tip 23K of
the blade.
The fore-aft length of a blade has traditionally been in the order of 1.75
inches from the front of the trash bar to the tip of the section, or 2.2
inches from the
front edge of the knife back to the tip of the section.
In this new arrangement, the fore-aft length L of the blade is increased
substantially. Thus the length of the cutting edges of each sickle blade or
blade is
greater than 2.2 inches. This can be as much as 2.6 inches and can lie in the
range
2.2 to 3.0 inches.
This also reduces the angle A of inward inclination of the cutting edge
from the typical 30 degrees relative to the center line (an equilateral
triangle) to an
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angle less than 30 degrees and typically of the order of 15 degrees and in the
range
15 to 30 degrees.
It is common practice for sickle blades to have the front edge as a
transverse straight edge in the order of 0.6 inches wide. The wide tip has the
potential for running down crop, thus leaving long uncut stems. In the present
invention the blade is designed with a pointed tip or front apex 23K, thus
eliminating
the problem.
The intention is therefore to provide a sickle blade which is as pointed
at the front apex 23K as reasonably practical. A sharp point is difficult to
obtain so
io that typically the front apex 23K is smoothly curved with a radius of
curvature R of a
curvature circle C less than 0.5 inches thus defining the front apex 23K which
is
sufficiently narrow to shed crop stalks to each side.
Each knife blade therefore has a front point portion in front of the
cutting edges which has side edges 23N, 23P converging to front apex where the
is apex and the side edges are shaped and arranged such that crop material
engaging
the point portion as the point portion is moved forwardly in the crop is shed
to one or
other side of the point portion for cutting and is not pushed forwardly by the
point
portion.
While this is the optimum arrangement, a practical construction may
20 have a transverse width of a straight line across the apex 23K which is
much less
than the conventional 0.7 inches and is typically less than 0.25 inches. This
narrow
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front edge is selected to be sufficiently narrow so that crop is shed to
either side and
not pushed forwardly as the blade moves forwardly.
The side edges 23N and 23P are inclined outwardly and away from the
apex at an angle Al relative to the center line 23H of the order of 35 degrees
and
certainly less than 45 degrees to the center line 23H.
The characteristics of the blade defined above where it is much
narrower than conventional and significantly longer places limitations on the
shape
and arrangement of the beveled and serrated edges 23F, 23G.
Thus the beveled edges 23F, 23G are reduced in width at 23Q as they
approach the front edge pointed portion 23K at the apex 23X leaving a strip
23R of
the upper surface between the beveled edges with parallel side edges of the
strip
23R. Thus at this strip 23R the beveled edge 23F, 23G becomes narrower and the
grooves 23L1 23M in the edge get shorter as the beveled edge approaches the
front
pointed portion 23X of the blade. The beveled edges 23F, 23G and the grooves
23L, 23M therein terminate at a position spaced from the front apex 23K to
define
the arrow head shaped portion 23X in front of the beveled edges which imparts
sufficient strength to the construction to allow the formation of the
serrations.
The cutting efficiency and therefore stubble length are also affected by
the width of the cutting edge 15B, 15C of the ledger surface 15A of the knife
guard
15. Generally, the width W1 between the edges 15B and 15C at the rear of the
cutting edge on the guard in the arrangement of the present invention is
substantially
increased from the conventional width of the order of 1.0 inches. Thus the
width
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W1 of each guard at a position thereon aligned with the rear end of the
cutting edge
of each blade is greater than 1.0 inches. The maximum width with i blade of
2.0
inches in width is slightly less than that of the width of the blade or
roughly 1.9
inches. Thus with a blade of this width, the width of the guards can be as
much as
1.9 inches and preferably lies in the range 1.2 to 1.9 inches. However where
the
blade is greater than 2.0 inches in width, the guard has a width which is
between 0.5
and 0.1 inches less than the width of the blade. The bottom guard also tapers
so
that its edges 15B and 15C lie closely adjacent the edges of the blade when
the
blade and guard are in the aligned position at the end of a stroke. Thus the
angle of
.. convergence of the edges 15A and 15B matches closely the angle A. This
leaves a
space S at the rear of the guards 15 at the trash bar 28 to avoid pinching
crop at this
location. This space S generally should be greater than 0.4 inches and
typically is of
the order of 0.5 inches.
Thus the cutting system is carried so that it moves across the ground
.. either closely in contact with the ground as shown or at a set cutting
height. in both
cases this determines a cutting height or nominal cutting distance from the
ground
with is the length of any crop stalk if cut efficiently and directly as it
reaches the
location between the blade and ledger surface. In Figure 2, the cutter bar
rests on
the ground at a skid plate 80 which holds the ledger surface 15A at the height
ND
.. from the ground. Typically this is of the order of 1.5 inches but this can
be varied
slightly by changing the angle of the cutter bar about a transverse axis by
changing
the angle of the header.
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Turning now to Figures 7 and 8, the shape of the pointed guard for use
in the present invention in conjunction with the pointed blade is shown and
described
in more detail as follows.
The knife guard 30 for use in a sickle cutting apparatus 10 includes the
S frame
structure 11, guard bar 13, sickle bar 24 and knife blades 23 as previously
described. Each the knife blades 23 has a cutting surface 23D for passing
across
the ledger surface 15A of the knife guards 151. Each of the knife blades has
on first
and second sides first and second side cutting edges as previously described
to
cooperate with shearing edges 152 of the guard guards 151.
n The
knife guard 151 includes a base portion 154 for mounting on the
cutter bar 13, a rear trash bar 28 in front of the base portion 154 and at
least one
guard finger 153. In this embodiment three fingers 153 are arranged in a row,
where
the finger or fingers 153 are mounted on the base portion 154 so that the
fingers are
arranged in a row along the cutter bar with a space 155 between each finger
and the
is next
allowing crop to enter the space up to a position of engagement with the rear
trash bar 28.
The guard fingers have the upwardly facing ledger surface 15A with
opposed side edges arranged to provide first and second shearing edges. The
guard fingers have a downwardly facing ground engaging surface 156 shaped and
20 arranged to provide protection for stone engagement as the fingers slide
over the
ground. That is each finger has sufficient strength to avoid breakage when
impacting stones and obstacles causing the cutter bar to rise if the impact is
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sufficient and extends over sufficient number of guard fingers to provide the
lifting
action. This shape of the ground engaging surface is well known to persons
skilled
in the art and includes a longitudinal rib which is generally triangular in
cross-section
on the underside of the upper part containing the ledger surface. The base of
the rib
thus forms an apex which runs over the ground to prevent upward forces from
snapping the guard finger at the ledger surface.
An upstanding transverse shoulder 157 is provided at a front edge of
the ledger surface 15A and extends upwardly to a top surface 158 of the finger
where the shoulder terminates. Thus there is no tang of conventional shape,
that is
no portion of the guard extending rearwardly over the ledger surface 15A from
the
shoulder 158. Above the ledge surface therefore the knife blades are free from
confinement by a conventional tang as used in a conventional pointed guard or
by a
cooperating upper guard finger of the type used in a stub guard as described
above.
A tip portion 159 in front of the ledger surface extends forwardly from
the shoulder 158 and defines a forwardmost generally pointed tip 160 for
engaging
crop in front of the ledger surface 15A.
A length Li of the ledger surface 15A from the trash bar 28 to the
shoulder 157 is greater than 2.0 inches or more preferably greater than 2.5
inches;
and a length L2 of the tip portion 159 from the shoulder to the tip is less
than 1.0
inch or more preferably less than or equal to 0.75 inches.
As defined previously, a center line spacing between each knife guard
finger and the next is less than 3.0 inches and preferably of the order of 2.0
inches.
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As defined previously, a width of each guard finger at the rear trash bar
is greater than 1.0 inches and more preferably is greater than 1.5 inches or
equal to
the maximum width which can be obtained while leaving a space at the trash bar
between the ledger surfaces in the range 0.25 to 0.5 inch or the distance
necessary
to avoid pinching of crop stalks between the ledger surfaces.
The side edges of the ledger surface 15A converge from the trash bar
28 to the shoulder 15 at an angle A4 greater than 10 degrees and preferably of
the
order of 12 degrees to a line LR at right angles to the trash bar or parallel
to the
center line CL. The angle A5 of the side edges at the shoulder increases so
that the
J.0 tip portion is shorter than would be the case if the angle A4 were
continued up to the
tip. However overall, it will be appreciated that a line joining the rear end
161 of the
side edge 151 of the ledger surface 15A and the tip 160 converges at an angle
greater than the 10 degrees of the side edge to a line at right angles to the
trash bar.
As the side edges converge at a relatively rapid angle from the base to
the tip, the ledger surface has a width W3 at the shoulder 157 of less than
0.75
inches and preferably of the order of 0.5 inches.
There is also provided a plurality of separate hold down members 162
arranged to engage the blades at every third spaced ones of the fingers. This
has a
base portion 163 mounted on the cutter bar 13 and a finger portion 164
extending
over the ledger surface of one of the fingers 14A.
Generally the cutting speed can be increased as the speed of the
sickle is increased. One limitation for the sickle speed is the stress that is
induced in
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the sickle drive and the knife back from the inertia loads resulting from the
acceleration of the sickle at the start of the stroke. These acceleration
loads are
proportional to the stroke length and to the square of the sickle speed.
Therefore for the same acceleration loads, if the stroke is decreased,
the speed can be increased by an amount represented by the following formula:
stroke2 = stroke1 X rpml A2 / rpm2 ^2
or in terms or speed:
rpm2 = (stroke1 X rpm1^2/ stroke2) A.5
For example for a typical 35 ft header and a single sickle knife driven
from one side, to achieve the same loads, if a sickle with a 3 inch stroke, is
run at
750 rpm, a sickle with a 2 inch stroke can be run at 918 rpm for the same
inertia
loads.
This distance of the cutting stroke is less than 3.0 inches and is more
preferably of the order of 2.0 inches. Typically the stroke can lie in the
range 1.5 to
2.5 inches since this provides a stroke length which allows an increase in the
cutting
reciprocation rate of the sickle bar. This rate is preferably greater than
900. A range
of 900 to 1200 rpm is particularly suitable depending on the length of the
sickle.
Thus, the maximum sickle speed is affected by the length of the sickle
assembly. Generally headers vary in width from 15ft to 45ft and are generally
available in single knife drive for widths up to 40ft. Therefore the length of
the sickle
can vary in length from 7.5 ft to 40ft.
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Where the maximum speed for a 40 ft single knife drive (SK) header
with a 3.0 inch stroke might be set at 600 rpm, the maximum speed for 15 ft
double
knife drive (OK) header might be set at 950 rpm.
Therefore in the case of a 2 inch cutting stroke, the cutting speed of
the new system will be increased by a percentage (22.4 %) over the current
system.
Depending on the length of the sickle, for same inertia loads, the sickle
speed can
be increased, as shown in Table 23:
It has been found with the current cutting system, that the increasing
the knife speed beyond a speed of about 950 rpm (1900 strokes per minute)
lo produces little improvement in cutting performance. It is suspected that
this is due to
the blunt face of the traditional knife blade or sickle section essentially
creating a
wall that prevents crop from entering the cutting area.
Turning now to the cutting efficiency obtained by the above geometry
of cutting system relative to prior art arrangements shown in Figure 9 to 13,
a
generic cutting system is shown in Figure 2A to show how cutting inefficiency
and
the associated increase in maximum stubble length arises.
Thus in Figure 2A, the cutting system is carried so that it moves across
the ground either closely in contact with the ground as shown or at a set
cutting
height. In both cases this determines a cutting height or nominal cutting
distance
ND from the ground with is the length of any crop stalk if cut efficiently and
directly
as it reaches the location between the blade and ledger surface. In Figure 2A,
the
cutter bar rests on the ground at a skid plate 80 which holds the ledger
surface 15A
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at the height ND from the ground. Typically this is of the order of 1.5 inches
but this
can be varied slightly by changing the angle of the cutter bar about a
transverse axis
by changing the angle of the header.
Cutting inefficiency arises where stalk S1 engages a blunt front edge
.. 23BL of the knife blade 23 so that it is pushed forwardly by the knife
blade rather
than reaching the side edges of the knife blade where it can be cut.
In conventional thinking it is understood that this effect is of little
importance in that the knife blade is moving rapidly side to side with the
expectation
that the sideways movement will immediately cause any such crop to be shed to
the
side away from the movement allowing it to be quickly cut.
However the analysis of the cutting system shows that, at high ground
speed, the forward movement has much more effect on the crop than the sideways
movement so that a band remains in contact with the blunt front edge L. This
crop is
then pushed forward forwardly and downwards without cutting until the crop is
shed
.. from the blade at the location where the blade reverses at the next guard
finger, or
at some point prior to that location, so that the crop can then enter into the
shearing
action on the second side of the blade.
Another analysis shows that, in each cycle of cutting crop, the side of
the blade which is not cutting will allow some stalks to move to a position
between
and the guard as the blade moves away from the guard sufficiently that the
blade
reaches a position in which the stalks engage the trash bar. Again therefore
these
stalks are pushed forwardly and downwards by the trash bar without cutting
until the
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blade comes back in the reverse direction to effect the shearing action of the
crop of
that second side of the guard.
It is known that sideways movement of the crop also occurs during
cutting. That is each stalk is carried sideways by the moving blade into the
shearing
action with the guard finger. This amount of movement varies depending on the
timing of the stalk entering the area to be cut and engaging the blade and the
side to
side position of the stalk as it enters the area. The amount of sideways
movement
will of course increase the length of the stalk as it is cut since the
position of the cut
is at a height of the stalk greater than the distance ND from the ground. The
lo analysis herein does not take into account this sideways movement since the
maximum stalk length which can be obtained by the sideways movement is always
less than the maximum stalk length which is obtained by the above described
forward movement.
However another benefit of the wider guard fingers is that the crop
moves to the side by a shorter distance before encountering the shearing
action at
the side edge of the guard.
It will be appreciated therefore that some stalks provide stubble length
of ND because they are cut without any forward pushing movement and some
stalks
are pushed forward to a length L2 or L3 where the actual stubble length is
equal to
the hypotenuse of the distance of forward movement before cutting occurs and
distance ND.
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As shown as an example in Figure 12A, the guard fingers 15, knife
blades 23 and the trash bar 28 are arranged so as to provide a cutting action
on the
crop in which in a first cutting stroke, each knife blade 23 moves across from
one
guard finger 151 to the next 152 in a first direction 231 so as to cut crop
located on
said first side of the knife blade 23 between the first cutting edge of the
knife blade
and the side 150 of the next guard finger 152 by the shearing action while
leaving
uncut crop located on the second side of the knife blade. In
a second cutting
stroke, each knife blade moves across from the next guard finger 152 to said
one
guard finger 151 in a second direction opposite to direction 231 so as to cut
crop
located on the second side of the knife blade between the second cutting edge
of
the knife blade and the guard finger 151 by the shearing action. The cutting
action
includes the previously uncut crop located on the first side of the blade 23,
while
leaving uncut crop located on the second side of the knife blade.
Turning now to Figures 9, 10 and 11 there is shown a stub guard
system similar to that previously described and shown in Figures 1 and 2 and
including many of the features previously defined above. In this embodiment,
however the system is a 3 inch system so that the tip to tip spacing of the
blades
and guards is 3 inches and the stroke of the sickle knife drive is also 3
inches so that
the blades reciprocate back and forth between a first points aligned with one
guard
to a point aligned with the next. Thus as shown in the stub guard system of
these
figures there is provided a bottom guard 50, a top hold down 51 and a set of
blades
52 carried on the reciprocating sickle bar.
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In this embodiment the shape and arrangement of these components
is substantially as previously described except that each guard element has
only two
fingers so that the pair of fingers of the bottom guard underlie the pair of
fingers of
the top hold down.
The pair of fingers of the top hold down are individually adjustable so
as to change the spacing SP between the finger 51A and the ledger surface of
the
guard finger 50A using the construction as shown and described in US patent
9622405 (Talbot) assigned to the present applicant and issued April 18 2017.
As best shown in Figures 10 and 11, the guard fingers 50A and blades
52 have lengths from the cutter bar arranged such that a forwardmost tip 50B
of the
guard finger 59A is forward of the tip 52B of the blade 52 and a forwardmost
tip 51B
of the hold down finger 51A is rearward of the tip 52B of the blade 52.
Preferably the tip of the guard finger is longer than the tip of the blade
by a distance up to 6.0 mm and preferably of the order of 3.0 mm.
Preferably the tip of the hold down finger is shorter than the tip of the
blade by a distance in the range 1.5 to 10.5 mm and preferably of the order of
5.0
mm.
That is the fingers form a conventional stub guard where there is no
component of the lower stub guard finger which is above the ledger surface.
However in this arrangement the tip 50B is located just in front of the tip of
the blade
rather than behind the tip of the blade as would be conventional. It has been
found
that this arrangement allows the clearing of the blade tip in tough cutting
conditions
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as does a normal stub guard system but in addition the slightly longer finger
cooperates with the pointed blade system described in detail herein where
there is
an additional point portion in front of the conventional beveled side cutting
edges of
the blade. This may improve the cutting action and may protect the point
against
damage while still allowing the clearing action of the crop from the front of
the
guards and blade which is obtained using a stub guard system.
Turning now to Figures 12 to 15 there is shown a pointed guard
system
similar to that previously described and shown in Figures 7 and 8 above.
In this arrangement however the pointed guard arrangement 60
includes a tang portion 62 overlying the ledger surface 61 so that the blade
52
passes through a slot 63 defined between the underside 65 of the tang portion
and
the ledger surface. The tang portion is connected to the tang portion in front
of the
slot by a pointed portion 64 of the pointed guard which converges to a front
tip in
front of the forward tip of the blade. The tang portion 62 extends rearwardly
over the
ledger surface from the point portion 64 to a rear edge 65 of the tang
portion. As
shown in Figure 12, the rear edge 65 is aligned with a trash bar 66 of the
guard
which extends outwardly to each side of the ledger surface. As described above
therefore the trash bar 66 forms or defines a transverse line across the
ledger
surface which constitutes the line of the rearmost cutting action of the blade
on the
ledger surface. This line is coincident with the rear edge of the sharpened
cutting
edge of the blade.
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As shown in Figure 12, the width of the tang portion at the rear edge
65 is equal to the width of the ledger surface of the guard at this point
which is
greater than 1.2 inches and more preferably of the order of 1.5 inches. This
wider
width of the guard and tang portion than is conventional in systems of this
type
provides an improved cutting action with the blade as described in more detail
above. This wider width of the tang portion also operates to provide improved
control
over the blade as it reciprocates through the slot. Even though the blade is
contacted by a hold down finger 68 between the guards, there is a tendency for
it to
rise so that the increased width of the tang portion ensures that it is
properly guided
into the slot as it approaches the slot from one side. Thus a width WT of the
tang
portion across the guard finger at the rear end of the tang portion is greater
than 1.2
inches and more preferably 1.5 inches.
As best shown in Figure 15, the lower surface 69 of the tang portion
includes a first portion 70 extending along the slot from the front of the
blade to a
junction point 72 where the first portion joins a second portion 71. The lower
surface
of the tang portion thus includes a first portion adjacent the tip portion
which is
generally parallel to the ledger surface and a second portion adjacent the
rear edge
which is inclined at an angle away from the ledger surface. The first portion
is planar
and parallel to the plane of the ledger surface. The second portion is also
planar
and is inclined upwardly away from the ledger surface from a transvers line at
the
junction 72 up to the rear tip 65. This shape of the slot surface of the
underside of
the tang portion provides effective control of the blade movement across the
ledger
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54
surface while also allowing the guard to be disconnected from the mounting
bolts
and tilted about the line at the junction 72 to lift the tip upwardly and to
lower the rear
edge downwardly to allow the guard to be pulled out forwardly with the blade
and
sickle bar 76 in place. This allows the rear of the guard to clear the sickle
bar to
move forwardly away from the cutter bar 77.
In one arrangement, the second portion of the tang portion at the
inclined angle is obtained by bending the tang upwardly at the junction line
72
relative to the first portion. This bending action occurs at the arrow 79 and
results in
a situation where both the upper and lower surfaces are inclined cause by the
bending of the material forming the tang portion.
As an alternative, the second portion of the tang portion tapers in depth
TD from the lower surface to an upper surface thereof toward the rear edge 65
thereof,
As shown in Figure 13, a length along the tang portion of second
portion 72 from the rear edge 65 to the first portion at the junction 72 is
shorter that a
length of the first portion 70 to the tip portion 64. Thus the main body of
the slot is
parallel to properly guide the blade and only a relatively short part of the
slot is
inclined upwardly.
Turning now to Figure 16, there is shown a blade 52 for use with the
systems of figure 9 and 12. It will be noted that the blade member which has a
base
portion 80 to attach to the sickle bar 76 forms a single blade and not a
double blade
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55
arrangement as shown and described previously herein. Each blade is therefore
a
separate component from each of the other blades with two side edges 81, 82 so
that the side edges of each blade lie immediately adjacent the side edges of
the next
adjacent blades when fastened to the sickle bar 76,
The base portion 80 has two countersunk holes 83 connected to slots
84 which communicate with the rear edge 85 of the mounting portion. This
allows
the blade to be pulled from the sickle bar 76 simply by loosening mounting
bolts 86
(Figure 13) sufficiently to allow the bolts to slide along the slots. This
arrangement is
described in more detail in US Patent 8893462 (Talbot) issued November 25 2014
and assigned to the present applicant, the disclosure of which may be
referenced for
further detail.
Each knife blade has a front point portion 87 in front of the side cutting
edges 88, 89 which front point portion has side edges 90, 91 converging to a
front
apex 92. This construction is substantially as previously described with the
exception that the wider blade of 3 inches rather than the previous shown 2
inches
provides a shorter and less pronounced point portion. However the point
portion has
the same construction relative to the beveled and serrated side edges as
previously
described. Also as shown in Figure 16, a length LB1 of each knife blade from
the
transverse line TL to the forwardmost tip 92 of the knife blade is greater
than 2.2
inches and preferably greater than 2.5 inches. As described before, the
transverse
line TL coincides with or is defined by the front of the trash bar and the
rear of the
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beveled edges which form the rearmost line of cutting action of the blade on
the
guard ledger surface.
Also as shown in Figure 16, each blade has a cut out opening 93
through the blade extending from a rear edge 99 of the opening adjacent to but
spaced from a rear edge 85 of the blade toward the tip of the blade. The cut
out
opening 93 has a rear edge 99 parallel to a rear edge 85 of the blade, two
side
edges 94, 95 substantially parallel at right angles to the rear edge 99 and
two
converging edges 96, 97 extending from the side edges to a forward apex 98.
This
shape takes out an amount of the material of the blade which ensures that the
blade
has approximately the same weight as a conventional 3 inch blade of a
conventional
length rather than the increased length herein. The shape and location of the
cut out
opening ensures that the material is removed without compromising the strength
of
the blade to meet its required loadings form the cutting action. The cut out
opening
does not interfere with the sliding action of the hold down fingers over the
upper
surface.
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