U.S. patent application number 13/743512 was filed with the patent office on 2013-11-21 for sickle guard shape for use in a sickle cutter system with increased ground speed.
This patent application is currently assigned to MACDON INDUSTRIES LTD.. The applicant listed for this patent is MACDON INDUSTRIES LTD.. Invention is credited to Francois R. Talbot.
Application Number | 20130305681 13/743512 |
Document ID | / |
Family ID | 48794339 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130305681 |
Kind Code |
A1 |
Talbot; Francois R. |
November 21, 2013 |
Sickle Guard Shape for Use in a Sickle Cutter System with Increased
Ground Speed
Abstract
In a sickle cutting system, it has been found 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 the
cutting stroke is reduced from the conventional length of 3.0
inches to a value of the order of 2.0 inches; the length of the
cutting edge of each knife blade is increased to a length greater
than 2.2 inches; the width at the rear of the ledger surface of
each guard is increased to greater than 1.0 inches; and the front
edge of the blade is formed with an apex to shed crop material to
one or other side of the apex.
Inventors: |
Talbot; Francois R.;
(Winnipeg, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MACDON INDUSTRIES LTD.; |
|
|
US |
|
|
Assignee: |
MACDON INDUSTRIES LTD.
Winnipeg
CA
|
Family ID: |
48794339 |
Appl. No.: |
13/743512 |
Filed: |
January 17, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61587843 |
Jan 18, 2012 |
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61664345 |
Jun 26, 2012 |
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61677169 |
Jul 30, 2012 |
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61677177 |
Jul 30, 2012 |
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Current U.S.
Class: |
56/257 ;
56/307 |
Current CPC
Class: |
A01D 34/18 20130101;
A01D 34/008 20130101; A01D 45/22 20130101; A01D 34/13 20130101;
A01D 34/14 20130101; A01D 43/00 20130101; A01D 34/28 20130101; A01D
41/12 20130101; A01D 34/02 20130101 |
Class at
Publication: |
56/257 ;
56/307 |
International
Class: |
A01D 34/18 20060101
A01D034/18; A01D 34/13 20060101 A01D034/13 |
Claims
1. A knife guard for use in a sickle cutting apparatus, the
apparatus 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 for receiving a plurality of stationary
knife guards mounted along the cutter bar and projecting forwardly
therefrom; a sickle bar mounted in transversely extending position
and being driven for reciprocating movement relative to said guard
fingers; 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 to cooperate with shearing edges of said guard
guards; the knife guard comprising: a base portion for mounting on
the cutter bar; at least one guard finger mounted on the base
portion so that the fingers are arranged in a row along the cutter
bar with a space between each finger and the next allowing crop to
enter the space; the guard finger having an upwardly facing ledger
surface with opposed side edges thereof arranged to provide first
and second shearing edges; a center line spacing between each guard
finger and the next being less than 3.0 inches; wherein a width of
each guard at a rearmost cutting portion of ledger surface is
greater than 1.5 inches.
2. The knife guard according to claim 1 wherein a width of each
guard at the rearmost cutting portion of ledger surface is greater
than 1.75 inches.
3. The knife guard according to claim 1 wherein a width of each
guard at the rearmost cutting portion of ledger surface is equal to
the maximum width which can be obtained while leaving a space at
the rearmost cutting portion of ledger surface between the ledger
surfaces of the order of 0.5 inch.
4. The knife guard according to claim 1 wherein a width of each
guard at the rearmost cutting portion of ledger surface is equal to
the maximum width which can be obtained while leaving a space at
the rearmost cutting portion of ledger surface between the ledger
surfaces which is of a width distance necessary to avoid pinching
of crop stalks between the ledger surfaces.
5. The knife guard according to claim 1 wherein the center line
spacing between each guard finger and the next is substantially
equal to 2.5 inches.
6. The knife guard according to claim 1 wherein the center line
spacing between each guard finger and the next is substantially
equal to 2.0 inches.
7. The knife guard according to claim 1 wherein a stroke length of
the reciprocating movement is equal to the center line spacing
between the guard fingers.
8. The knife guard according to claim 1 wherein the guard finger
has a downwardly facing ground engaging surface shaped and arranged
to provide protection for stone engagement.
9. A sickle cutting apparatus 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 for
receiving a plurality of stationary knife guards mounted along the
cutter bar and projecting forwardly therefrom; a sickle bar mounted
in transversely extending position and being driven for
reciprocating movement relative to said guard fingers; 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 to
cooperate with shearing edges of said guard guards; and a plurality
of knife guards according to claim 1.
10. The sickle cutting apparatus according to claim 9 wherein at
the position in a stroke of the reciprocating movement 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.
11. The sickle cutting apparatus according to claim 9 wherein 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.
12. The sickle cutting apparatus according to any claim 11 wherein
the front point portion has side edges which are not sharpened.
13. The sickle cutting apparatus according to claim 9 wherein there
is provided a plurality of separate hold down members arranged to
engage the blades at the fingers.
14. The sickle cutting apparatus according to claim 9 wherein each
knife guard comprises a stub guard with a lower member defining the
finger and an upper member overlying the finger with the knife
blade having a length so as to project forwardly from a front tip
of the upper and lower members.
Description
[0001] This application claims the benefit under 35 USC 119(e) of
Provisional Applications U.S. 61/587,843 filed Jan. 18, 2012; U.S.
61/664,345 filed Jun. 26, 2012; 61/677,169 filed Jul. 30, 2012 and
U.S. 61/677,177 filed Jul. 30, 2012.
[0002] This invention relates generally to a sickle guard for a
sickle knife cutter system for harvesting crop with improved
cutting action which may allow increased ground speed while
maintaining cutting efficiency and/or stubble height at an
acceptable level.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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 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.
[0005] 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.
[0006] 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 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.
[0007] 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 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.
[0008] 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.
[0009] 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 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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 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.
[0015] 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
[0016] It is one object of the present invention to provide a guard
for a sickle cutting apparatus which can provide an improvement in
cutting efficiency leading to a possible increase in ground
speed.
[0017] According to the invention there is provided a knife guard
for use in a sickle cutting apparatus 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 for
receiving a plurality of stationary knife guards mounted along the
cutter bar and projecting forwardly therefrom; a sickle bar mounted
in transversely extending position and being driven for
reciprocating movement relative to said guard fingers; 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 to
cooperate with shearing edges of said guard guards; comprising:
[0018] a base portion for mounting on the cutter bar;
[0019] at least one guard finger mounted on the base portion so
that the fingers are arranged in a row along the cutter bar with a
space between each finger and the next allowing crop to enter the
space;
[0020] the guard finger having an upwardly facing ledger surface
with opposed side edges thereof arranged to provide first and
second shearing edges;
[0021] a center line spacing between each guard finger and the next
being less than 3.0 inches;
[0022] wherein a width of each guard at a rearmost cutting portion
of ledger surface is greater than 1.5 inches.
GENERAL DESCRIPTION
[0023] 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:
[0024] a) The distance between the center line of the guards which
is generally equal to the distance between the center line of the
blades is reduced from the conventional length of 3.0 inches. 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, the reduced
center line distance has been shown to provide a significant
advantage.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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 10 mph and up to 14 mph and to harvest soy
beans at greater than 5 mph and up to 6 or 7 mph.
[0029] 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.
Blade Length
[0030] 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 and typically of the order of or
greater than 2.75 inches.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] The term "trash bar" as used herein 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".
[0036] 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.
[0037] Thus in one example the blade has a width of 2.0 inches at
the base and a length from the front of the trash bar to the tip of
2.5 inches.
Pointed Blade Tip
[0038] 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 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.
[0039] 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 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.
[0040] 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.
[0041] The angle of the side edges of the front point portion can
be greater and is typically in the range 30 to 45 degrees and
preferably of the order of 35 degrees.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] Preferably the beveled side sedges are serrated in a
direction at right angles to a forward direction.
[0046] Preferably the pointed portion has a thickness at the apex
equal to that of the blade.
[0047] 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.
[0048] Preferably at this strip the beveled edges become narrower
as the beveled edge approaches the front pointed portion of the
blade.
[0049] 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.
[0050] 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.
[0051] 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 2.5 inches and more preferably greater than
2.75 inches.
[0052] Preferably the front point portion has side edges which are
not sharpened.
[0053] 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.
Blade Shape
[0054] The characteristics of the blade defined above where it is
much narrower than conventional, 2.0 inches as opposed to 3.0
inches, and significantly longer, 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.
[0055] 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.
Width of Guard Cutting Edge
[0056] 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. 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 has a width which is between
0.5 and 0.1 inches less than the width of the blade.
[0057] Thus the arrangement provided herein provides a center line
spacing between each guard finger and the next which is 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.
[0058] 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 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.
[0059] Preferably the stroke length is equal to the center line
spacing between the knife blades.
[0060] 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.
[0061] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIG. 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.
[0063] FIG. 2 is a cross-sectional view along the lines 2-2 of FIG.
1.
[0064] FIG. 3 is top plan view of a knife blade for use in the
sickle knife of FIG. 1.
[0065] FIG. 4 is a side elevational view along of the knife blade
of FIG. 3.
[0066] FIG. 5 is top plan view of one knife blade of FIG. 3 on an
enlarged scale showing the angles of the side edges for different
length blades.
[0067] FIG. 6 is top plan view of a knife blade of the type of FIG.
3 showing a different width blade.
[0068] FIG. 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.
[0069] FIG. 8 is a cross-sectional view along the lines 8-8 of FIG.
7.
DETAILED DESCRIPTION
[0070] In FIGS. 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.
[0071] 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 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.
[0072] 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.
[0073] The knife guards shown in FIGS. 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] In some cases the bar reciprocates by a distance S1 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.
[0078] The following table shows the set stroke rate in rpm to be
used in the calculation of inefficiency for different speeds and
stroke length.
TABLE-US-00001 6 MPH 10 MPH 14 MPH Typical RPM Typical RPM Typical
RPM 2'' stroke 735 918 1102 3'' stroke 600 750 900 4'' stroke 520
650 779
[0079] 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 FIG. 3, but
individual blades may be provided or in some cases the blades may
have more than two on the same base.
[0080] 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.
[0081] 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.
[0082] 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 adjacent and generally in contact or at
least closely adjacent to provide a shearing action on the
crop.
[0083] 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 FIG. 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.
[0084] 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.
[0085] The disclosures of the following documents of the present
Applicants are incorporated herein by reference or 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.
[0086] U.S. Pat. No. 7,328,565 (Snider) issued Feb. 12, 2008;
[0087] U.S. Pat. No. 4,894,979 (Lohrentz) issued Jan. 23, 1990
[0088] U.S. Pat. No. 4,909,026 (Molzahn) issued Mar. 20, 1990.
[0089] U.S. Pat. No. 6,962,040 (Talbot) issued Nov. 8, 2005.
[0090] U.S. application Ser. No. 13/680,557 filed Nov. 19, 2012
based on a Provisional application 61/577,427 filed Dec. 19, 2011
(Talbot) relating to an adjustable hold down.
[0091] In FIG. 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 S1 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.
[0092] 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 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.
[0093] 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.
[0094] Typically each of the knife blades is generally triangular
in shape with 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 23D 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.
[0095] 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 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.
[0096] 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.
[0097] At the position in the stroke shown in FIG. 1 where the
center line C of the knife blades is aligned with the center line
C1 of the guard fingers, the side cutting edges of the knife blades
23F, 23G substantially directly overlie the side edges 15B, 15C of
the ledger surface 15A.
[0098] 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 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.
[0099] As shown in FIGS. 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 FIG.
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 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.
[0100] 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.
[0101] As shown in FIGS. 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 FIG. 6 (not to scale) a wider spacing of 2.5 inches
is shown. In FIG. 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.
[0102] As shown in FIGS. 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
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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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 edges of
the front portion are arranged relative to a center line of the
blade at an angle of the order of 20 degrees.
[0107] As shown in FIG. 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.
[0108] This distance D 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 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 FIG. 2, is
generally triangular in shape. In the example shown, the blade 23
forms a double 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.
[0109] 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 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.
[0110] 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.
[0111] 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.
[0112] 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 angle less than 30 degrees and
typically of the order of 15 degrees and in the range 15 to 30
degrees.
[0113] 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.
[0114] 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 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.
[0115] 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 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.
[0116] While this is the optimum arrangement, a practical
construction may 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 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.
[0117] The side edges 23N and 23P are inclined outwardly and away
from the apex at an angle A1 relative to the center line 23H of the
order of 35 degrees and certainly less than 45 degrees to the
center line 23H.
[0118] 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.
[0119] 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 23L, 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.
[0120] 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 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 a 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.
[0121] 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 FIG.
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.
[0122] Turning now to FIGS. 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.
[0123] The knife guard 30 for use in a sickle cutting apparatus 10
includes the 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.
[0124] 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 next allowing crop to enter the space up to a
position of engagement with the rear trash bar 28.
[0125] 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 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 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.
[0126] 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.
[0127] 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.
[0128] A length L1 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.
[0129] 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.
[0130] 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.
[0131] 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 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.
[0132] 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.
[0133] 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.
* * * * *