U.S. patent application number 12/109758 was filed with the patent office on 2009-10-29 for integrated draper belt support and skid shoe in an agricultural harvesting machine.
Invention is credited to John Andrios, Bruce A. Coers, Benjamin M. Lovett, Kyle A. Meeske, Corwin M. Puryk.
Application Number | 20090266044 12/109758 |
Document ID | / |
Family ID | 40796280 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266044 |
Kind Code |
A1 |
Coers; Bruce A. ; et
al. |
October 29, 2009 |
INTEGRATED DRAPER BELT SUPPORT AND SKID SHOE IN AN AGRICULTURAL
HARVESTING MACHINE
Abstract
A cutting platform for use with an agricultural harvesting
machine includes at least one platform section. Each platform
section has a cutterbar assembly movable in a localized manner in
upwards and downwards directions, an endless belt with a leading
edge, and a plurality of skid shoes. Each skid shoe extends
rearwardly from the cutterbar assembly and has an upper surface
defining a belt support for the leading edge of the endless
belt.
Inventors: |
Coers; Bruce A.; (North
Hillsdale, IL) ; Meeske; Kyle A.; (East Moline,
IL) ; Andrios; John; (Geneseo, IL) ; Lovett;
Benjamin M.; (Colona, IL) ; Puryk; Corwin M.;
(East Moline, IL) |
Correspondence
Address: |
Taylor & Aust, P.C/Deere & Company
P.O. Box 560
Avilla
IN
46710
US
|
Family ID: |
40796280 |
Appl. No.: |
12/109758 |
Filed: |
April 25, 2008 |
Current U.S.
Class: |
56/208 |
Current CPC
Class: |
A01D 57/20 20130101;
A01D 41/14 20130101; A01D 67/00 20130101; A01D 61/002 20130101 |
Class at
Publication: |
56/208 |
International
Class: |
A01D 67/00 20060101
A01D067/00 |
Claims
1. A cutting platform for use with an agricultural harvesting
machine, comprising: at least one platform section, each said
platform section including: a cutterbar assembly movable in a
localized manner in upwards and downwards directions; an endless
belt having a leading edge; and a plurality of skid shoes, each
said skid shoe extending rearwardly from said cutterbar assembly
and having an upper surface defining a belt support for said
leading edge of said endless belt.
2. The cutting platform of claim 1, wherein each said platform
section includes a plurality of skid plates, each said skid plate
being detachably connected to a lower surface of a respective said
skid shoe.
3. The cutting platform of claim 2, wherein each said skid shoe is
a bent metal skid shoe.
4. The cutting platform of claim 3, wherein each said skid shoe has
a hollow cavity in an area adjacent said belt support.
5. The cutting platform of claim 4, wherein each said belt support
is generally L-shaped in cross section.
6. The cutting platform of claim 4, wherein each said skid plate
has at least one reinforcing rib extending into said hollow cavity
and terminating adjacent said lower surface of said belt
support.
7. The cutting platform of claim 6, wherein each said skid plate
has a plurality of interconnected reinforcing ribs extending into
said hollow cavity and terminating adjacent a lower side of said
belt support.
8. The cutting platform of claim 1, wherein said skid shoes are
movable relative to each other.
9. The cutting platform of claim 8, wherein each said skid shoe
includes a laterally extending shield with a lower end which is
positioned below a respective said belt support.
10. The cutting platform of claim 9, wherein each said shield has a
lateral end with an overlap, each said overlap overlapping an
adjacent said skid shoe.
11. The cutting platform of claim 10, wherein each said overlap
includes a bent lip.
12. The cutting platform of claim 2, wherein each said skid shoe is
made from metal, and each said skid plate is made from plastic.
13. The cutting platform of claim 12, wherein each said skid shoe
is a stamped metal part, and each said skid plate is a cast plastic
part.
14. A skid shoe for use with a cutting platform in an agricultural
harvesting machine, said skid shoe comprising: a forward end for
attachment with a cutterbar assembly, a lower surface positionable
in association with a ground surface over which the harvesting
machine traverses, and an upper surface defining a belt support for
a leading edge of an endless belt.
15. The skid shoe of claim 14, including a skid plate detachably
connected to said lower surface of said skid shoe.
16. The skid shoe of claim 15, wherein said skid shoe is a bent
metal skid shoe.
17. The skid shoe of claim 16, wherein said skid shoe has a hollow
cavity in an area adjacent said belt support.
18. The skid shoe of claim 17, wherein said belt support is
generally L-shaped in cross section.
19. The skid shoe of claim 17, wherein said skid plate has at least
one reinforcing rib extending into said hollow cavity and
terminating adjacent said lower surface of said belt support.
20. The skid shoe of claim 19, wherein said skid plate has a
plurality of interconnected reinforcing ribs extending into said
hollow cavity and terminating adjacent a lower side of said belt
support.
21. The skid shoe of claim 14, wherein said skid shoe includes a
laterally extending shield with a lower end which is positioned
below said belt support.
22. The skid shoe of claim 21, wherein said shield has a lateral
end with an overlap.
23. The skid shoe of claim 22, wherein said overlap includes a bent
lip.
24. The skid shoe of claim 14, wherein said skid shoe is made from
metal, and said skid plate is made from plastic.
25. The skid shoe of claim 24, wherein said skid shoe is a stamped
metal part, and said skid plate is a cast plastic part.
26. An agricultural harvesting machine, comprising: a base unit
including a feeder housing; and a cutting platform attached to said
feeder housing, said cutting platform including at least one
platform section, each said platform section having: a cutterbar
assembly movable in a localized manner in upwards and downwards
directions; an endless belt having a leading edge; and a plurality
of skid shoes, each said skid shoe extending rearwardly from said
cutterbar assembly and having an upper surface defining a belt
support for said leading edge of said endless belt.
27. The agricultural harvesting machine of claim 26, wherein each
said platform section includes a plurality of skid plates, each
said skid plate being detachably connected to a lower surface of a
respective said skid shoe.
28. The agricultural harvesting machine of claim 26, wherein each
said skid shoe is a bent metal skid shoe with a hollow cavity in an
area adjacent said belt support, and each said skid plate has at
least one reinforcing rib extending into said hollow cavity and
terminating adjacent a lower side of said belt support.
29. The agricultural harvesting machine of claim 28, wherein each
said skid plate has a plurality of interconnected reinforcing ribs
extending into said hollow cavity and terminating adjacent a lower
surface of said belt support.
30. The agricultural harvesting machine of claim 26, wherein said
skid shoes are movable relative to each other, and include a
laterally extending shield with a lower end which is positioned
below a respective said belt support.
31. The agricultural harvesting machine of claim 30, wherein each
said shield has a lateral end with an overlap, each said overlap
overlapping an adjacent said skid shoe.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to agricultural harvesting
machines, and, more particularly, to agricultural combines
including a draper cutting platform.
BACKGROUND OF THE INVENTION
[0002] An agricultural harvesting machine such as a combine
includes a head and a feeder housing which remove the crop material
from the field, gather the crop material and transport the crop
material to a separator. In the case of thinner stemmed crops such
as soybeans, wheat, etc. which may be cut with a sickle bar
carrying a plurality of knives, the head may also be known as a
cutting platform. The separator removes the grain crop material
from the non-grain crop material. The grain is cleaned and
deposited in a grain tank. When the grain tank becomes full, an
unloading auger which is positioned alongside the combine during
harvesting is moved to the unloading position in which the auger
extends approximately perpendicular to the longitudinal axis of the
combine. The combine drives alongside a vehicle into which the
grain is to be unloaded, such as a semi-trailer, and the unloading
auger is actuated to discharge the grain into the vehicle.
[0003] A cutting platform may generally be of two types. One type
typically has a sheet metal floor with a dual feed auger near the
rear of the cutting platform for feeding the crop material
longitudinally to the feeder housing. A cutting platform of this
type with auger feed is more common.
[0004] Another type of cutting platform, also known as a draper
platform, utilizes a flat, wide belt, referred to as a draper or
draper belt to convey crop material. The arrangement and number of
belts vary among platforms. One style of draper platform has two
side belts that convey crop material longitudinally, to the center
of the platform, where a center feed belt moves the crop material
laterally into the feeder housing. Each belt is wrapped around a
pair of rollers, one being a drive roller and the other being an
idler roller. An example of this type draper arrangement is
disclosed in U.S. Pat. No. 6,202,397, which is assigned to the
assignee of the present invention.
[0005] An advantage of a draper platform is that larger amounts of
crop material can be transported without plugging, etc. For
example, with wide platforms approaching 40 feet or even larger,
the amount of crop material transported to the feeder housing can
be substantial. With an auger feed platform, the crop material may
bind between the auger and the back wall of the platform. In
contrast, with a draper platform, the crop material is carried on
top of the belt with less chance for plugging.
[0006] Draper platforms currently in use have a rigid framework not
allowing the framework to flex to any appreciable extent during
use. The draper platform can be placed in a "float" position such
that the cutterbar at the leading edge does not dig into the
ground, but the leading edge of the platform itself cannot flex
across the width of the platform as a result of uneven ground
terrain. This results in some crop material being missed in ground
depressions, etc., while also possibly causing a part of the
cutterbar to dig into localized ground elevations (e.g., small
mounds, etc.). Of course, missed crop material directly translates
into missed revenue, and localized gouging of soil can cause
additional repair expenses resulting from broken knives, knife
guards, etc.
[0007] Rigid platforms as described above typically include skid
shoes at the bottom of the leading edge. The skid shoes are
generally angled rearwardly and downwardly from the leading edge
and are movable upwards and downwards at least slightly relative to
each other. The skid shoes are typically stand alone components
with sheet metal extending between and covering the bottom, leading
edge of the skid shoes. In the case of a draper platform, belt
carriers which are separate from the skid shoes carry the return
run of the draper belt.
[0008] What is needed in the art is a draper platform which better
follows the ground contour during operation.
SUMMARY OF THE INVENTION
[0009] The invention comprises, in one form thereof, a cutting
platform for use with an agricultural harvesting machine, including
at least one platform section. Each platform section includes a
cutterbar assembly movable in a localized manner in upwards and
downwards directions, an endless belt with a leading edge, and a
plurality of skid shoes. Each skid shoe extends rearwardly from the
cutterbar assembly and has an upper surface defining a belt support
for the leading edge of the endless belt.
[0010] The invention comprises, in another form thereof, a skid
shoe for use with a cutting platform in an agricultural harvesting
machine. The skid shoe includes a forward end for attachment with a
cutterbar assembly, a lower surface positionable in association
with a ground surface over which the harvesting machine traverses,
and an upper surface defining a belt support for a leading edge of
an endless belt.
[0011] The invention comprises, in yet another form thereof, an
agricultural harvesting machine, including a base unit with a
feeder housing, and a cutting platform attached to the feeder
housing. The cutting platform includes at least one platform
section. Each platform section has a cutterbar assembly movable in
a localized manner in upwards and downwards directions, an endless
belt having a leading edge, and a plurality of skid shoes. Each
skid shoe extends rearwardly from the cutterbar assembly and has an
upper surface defining a belt support for the leading edge of the
endless belt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a fragmentary, top view of an agricultural combine
including an embodiment of a draper platform of the present
invention;
[0013] FIG. 2 is a fragmentary, perspective view of the
agricultural combine of FIG. 1;
[0014] FIG. 3 is a fragmentary, perspective view of the cutting
platform shown in FIGS. 1 and 2;
[0015] FIG. 4 is a fragmentary, top view of the leading edge of the
cutting platform shown in FIGS. 1-3;
[0016] FIG. 5 is a fragmentary, front perspective view of the
leading edge of the cutting platform shown in FIGS. 1-3;
[0017] FIG. 6 is a fragmentary, rear perspective view of the
leading edge shown in FIG. 5;
[0018] FIG. 7 is a fragmentary, side sectional view of the leading
edge of FIGS. 5 and 6; and
[0019] FIG. 8 is an exploded view of the skid shoe and skid plate
shown in FIGS. 5-7.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to the drawings, and, more particularly to
FIGS. 1-4, there is shown an agricultural harvesting machine in the
form of a combine 10 including an embodiment of a cutting platform
12 of the present invention. Combine 10 includes a feeder housing
14 which is detachably coupled with cutting platform 12. Feeder
housing 14 receives the crop material from cutting platform 12,
both grain and non-grain crop material, and transports the crop
material to a separator within combine 10 in known manner (not
shown). The grain crop material is separated from the non-grain
crop material, cleaned and transported to a grain tank. The
non-grain crop material is transported to a chopper, blower, etc.
in known manner and distributed back to the field.
[0021] Cutting platform 12 generally includes a plurality of
platform sections 16, 18 and 20, a cutterbar assembly 22 and a reel
assembly 24. In the embodiment shown, platform section 16 is a
center platform section, platform section 18 is a first wing
platform section, and platform section 20 is a second wing platform
section. Although shown with three platform sections, cutting
platform 12 may be configured with more or less platform sections,
depending upon the particular application.
[0022] Each platform section 16, 18 and 20 generally includes a
frame 26, a plurality of float arms 28 coupled with a respective
frame 26, a cutterbar 30 carried by the outboard ends of respective
float arms 28, an endless belt 32, and a plurality of belt guides
34. The frame 26 of first wing platform section 18 and second wing
platform section 20 are each pivotally coupled with center platform
section 16, such that the outboard ends of first wing platform
section 18 and second wing platform section 20 can move up and down
independent from center platform section 16. To that end, a lift
cylinder 36 coupled between the frame of combine 10 and feeder
housing 14 lifts the entire cutting platform 12, a first tilt
cylinder 38 coupled between the respective frame 26 of first wing
platform section 18 and center platform section 16 pivotally moves
first wing platform section 18 relative to center platform section
16, and a second tilt cylinder 40 coupled between the respective
frame 26 of second wing platform section 20 and center platform
section 16 pivotally moves second wing platform section 20 relative
to center platform section 16.
[0023] Cutterbar assembly 22 includes two cutterbars 30 carried at
the outboard ends of float arms 28 (i.e., at the leading edge of a
platform section 16, 18 or 20). Each cutterbar 30 includes a
plurality of knives 42 carried by a bar (not specifically shown).
The particular type of knife can vary, such as a double blade knife
(as shown) or a single blade knife. The bar is formed from a metal
which is flexible to an extent allowing a desired degree of flexure
across the width of cutting platform 12. In the embodiment shown, a
majority of each cutterbar 30 is carried by a respective first wing
platform section 18 or second wing platform section 20, with a
lesser extent at the adjacent inboard ends of each cutterbar 30
being carried by center platform section 16. Cutterbars 30 are
simultaneously driven by a single knife drive 44, providing
reciprocating movement in concurrent opposite directions between
cutterbars 30.
[0024] A plurality of knife guards 46 are positioned in opposition
to knives 42 for providing opposing surfaces for cutting the crop
material with knives 42. A plurality of keepers 48 spaced along
cutterbars 30 have a distal end above cutterbars 30 for maintaining
cutterbars 30 in place during reciprocating movement.
[0025] Float arms 28 may be pivoted at their connection locations
with a respective frame 26. A float cylinder 50 coupled between a
respective frame 26 and float arm 28 may be used for raising or
lowering the outboard end of float arm(s) 28 at the leading edge of
cutting platform 12. Each float cylinder 50 may also be placed in a
"float" position allowing the connected float arm 28 to generally
follow the ground contour during operation. More particularly, each
float cylinder 50 is fluidly connected with an accumulator 52
carried by a platform section 16, 18 or 20. Accumulator 52 allows
fluid to flow to and from attached float cylinders 50 such that no
pressure build-up occurs. In this manner, the rams associated with
each float cylinder 50 are free to move back and forth
longitudinally, thereby allowing float arms 28 to follow the ground
contour. When not in a float mode, float cylinders 50 can be
actuated to move float arms 28 in an upward or downward direction.
In the embodiment shown, each float cylinder 50 is a hydraulic
cylinder, but could possibly be configured as a gas cylinder for a
particular application.
[0026] Each float arm 28 is also associated with a respective
roller 54. The plurality of rollers 54 for each platform section
16, 18 and 20 carry and are positioned within a loop of a
respective endless belt 32. At the inboard end of first wing
platform section 18 and second wing platform section 20 is a driven
roller, and at the outboard end of first wing platform section 18
and second wing platform section 20 is an idler roller. The rollers
positioned between the inboard drive roller and outboard idler
roller at each float arm 28 also function as idler rollers. It will
be appreciated that the number of float arms 28, and thus the
number of rollers 54, may vary depending upon the overall width of
cutting head 12 transverse to the travel direction.
[0027] Reel assembly 24 includes two reels 56, center reel support
arm 58 and a pair of outer reel support arms 60. Outer reel support
arms 60 are pivotally coupled at one end thereof with an outboard
end of a respective first wing platform section 18 or second wing
platform section 20. Outer reel support arms 60 rotationally carry
a respective reel 56 at an opposite end thereof. Each outer reel
support arm 60 may be selectively moved up and down using a
hydraulic cylinder, and the pair of hydraulic cylinders are
typically coupled in parallel so that they move together upon
actuation.
[0028] Center reel support arm 58 is pivotally coupled at one end
thereof with center platform section 16 above the opening leading
to feeder housing 14. Center reel support arm 58 rotationally
carries an inboard end of each reel 56 at an opposite end thereof.
A hydraulic motor 62 or other suitable mechanical drive
rotationally drives each reel 56. More particularly, hydraulic
motor 62 drives a common drive shaft 64 through a chain and
sprocket or other suitable arrangement (not shown). The rotational
speed of reels 56 can be adjusted by an operator by adjusting the
rotational speed of hydraulic motor 62.
[0029] Center reel support arm 58 may be selectively moved up and
down using a hydraulic cylinder 66. Center reel support arm 58 is
movable independently from outer reel support arms 60. To
accommodate this independent movement, drive shaft 64 driven by
hydraulic motor 62 is coupled at each end thereof via a universal
joint 68 with a respective reel 56. This independent movement of
center reel support arm 58 can be accomplished manually using a
separate actuating switch or lever in operator's cab 70, or
automatically using an electronic controller 72 located within cab
70 or other suitable location.
[0030] According to an aspect of the present invention, each
platform section 16, 18 and 20 has a leading edge which is
configured to allow cutterbar assembly 22 to flex an appreciable
extent in a localized manner across the width of cutting platform
12.
[0031] Referring to FIGS. 4-8, each float arm 28 has a distal end
adjacent the leading edge of cutting platform 12. The float arms 28
associated with each respective platform section 16, 18 and 20 are
mounted with a corresponding flexible substrate 74 extending
substantially across the width of that particular platform section
16, 18 or 20. Flexible substrate 74 for each particular platform
section 16, 18 and 20 in essence forms the backbone to which the
other modular components (to be described hereinafter) are mounted
and allows flexibility of the platform section across the width
thereof. In the embodiment shown, flexible substrate 74 is a steel
plate with various mounting holes formed therein, and has a modulus
of elasticity providing a desired degree of flexibility. The
geometric configuration and material type from which flexible
substrate 74 is formed may vary, depending upon the
application.
[0032] The distal end of each float arm 28 is fastened to a knife
guard 46, flexible substrate 74, crop ramp 76 and hold down 48.
Cutterbar 30, including blades 44 carried by bar 78, is
reciprocally carried by knife guards 46. Hold downs 48 which are
spaced across the width of cutterbar 30 retain bar 78 within the
corresponding grooves formed in knife guards 46.
[0033] Crop ramps 76 (FIG. 4) are overlapped but not rigidly
attached to each other, thereby allowing flexure during harvesting
operation. Each crop ramp 76 forms an upper ledge positioned above
endless belt 32 which assists in maintaining the crop material on
endless belt 32 as it is transported toward feeder housing 14. In
the embodiment shown in FIG. 4, crop ramp 76 has a flat, angled
orientation to assist in transport of the crop material from
cutterbar assembly 22 to endless belt 32. For certain applications,
it may be possible to eliminate crop ramps 76.
[0034] Belt guides 80 are formed with both a smooth upper
transition and a smooth lower transition between adjacent belt
guides 80, resulting in no or little accumulation of crop material
above the belt guides, and no extra wear to the endless belt 32
below the belt guides. More particularly, each belt guide 80 has a
rear edge 82 with an upper surface 84 and a lower surface 86. Lower
surface 86 partially overlies a leading edge 88 of endless belt 32.
Upper surface 84 and lower surface 86 each have a continuous,
uninterrupted contour. That is, there are no abrupt discontinuities
such as recesses or projections which might tend to accumulate crop
material (on top) or wear the endless belt (below). In the
embodiment shown, upper surface 84 and lower surface 86 are each
generally planar, but could also be formed with a slight curvature
(e.g., simple or compound curvature).
[0035] The direction of overlap between adjacent belt guides 80 is
generally opposite to the travel direction of endless belt 32.
However, by providing a smooth lower transition between adjacent
belt guides 80, there is no undue wear to either the lip 94 or the
endless belt 32. Further, the direction of overlap between adjacent
belt guides 80 is in the same direction as the crop material
movement across the upper surfaces thereof, resulting in little or
no accumulation of crop material on top of belt guides 80.
[0036] Skid shoes 100 (FIGS. 5-8) are mounted at the forward end to
flexible substrate 74, and thus extend rearwardly from cutterbar
assembly 22. Skid plates 102 are detachably mounted to skid shoes
100 using fasteners 104, such as rivets, bolts or screws. Skid
shoes 100 and skid plates 102 act in a conventional manner as a
skid shoe below cutterbar assembly 22, but in addition also include
an integral belt support 106 for supporting the leading edge 88 of
the return run of endless belt 32.
[0037] More particularly, each skid shoe 100 includes an upper
surface 108 defining belt support 106. Belt support 106 has a
generally L-shaped cross-sectional configuration with a belt
carrying surface 110 which is oriented generally parallel to the
return run of the endless belt 32 when the leading edge of cutting
platform 12 is in a lowered, working position. By combining belt
support 106 into skid shoe 100, a separate component part in the
form of a separate belt carrier for the return run of the endless
belt 32 is eliminated. Since numerous belt carriers are utilized
along the length of the return run of the endless belt, this
results in considerable part reduction, simplicity of design, and
cost savings.
[0038] Skid shoes 100 are movable relative to each other and are
made as a bent metal part, preferably formed as a stamped metal
part from sheet metal to reduce manufacturing costs. Configured as
such, each skid shoe 100 includes a hollow cavity 112 at a lower
surface 114 thereof. Each skid plate 102 is mounted to the lower
surface 114 of a respective skid shoe 100, and covers hollow cavity
112. During use it is possible (and in fact likely) that skid
plates 102 will impinge upon various ground projections, such as
rocks, sticks, hard dirt clods, etc. To inhibit deformation upon
impact with such objects, each skid plate 102 includes one or more
reinforcing ribs 116 which extend into hollow cavity 112 and
terminate adjacent lower surface 114 of hollow cavity 112. In the
embodiment shown, each skid plate 102 includes a plurality of
interconnected reinforcing ribs 116 which extend into hollow cavity
112 and terminate adjacent lower surface 114 of hollow cavity 112.
Reinforcing ribs 116 allow skid plate 102 to be formed from
plastic, such as with a casting process.
[0039] Each skid shoe 100 also includes an integral and laterally
extending shield 118. Shield 118 has a lower end 120 which is
positioned below the belt carrying surface 108 of belt support 106
so as to prevent crop and other material from impinging upon or
accumulating at the leading edge of endless belt 32. Shield 118 has
a lateral end with an overlap 122 which is configured to overlap
but allow movement relative to an adjacent skid shoe 100. Overlap
122 includes a bent lip (not numbered) which overlaps with an
adjacent skid shoe 100.
[0040] During harvesting operation, float arms 28 are placed in a
float state allowing free upward and downward movement as combine
10 traverses over the ground surface. Cutterbar assembly 22 moves
up and down with float arms 28 on a localized basis, and crop ramps
76 and belt guides 80 move relative to each other to allow the
flexibility at the leading edge of each platform section 16, 18 and
20. Belt guides 80 also cause each belt 32 to follow the cutterbar
assembly by holding down on the upper surface of the belt as
cutterbar assembly 22 locally dips downward. This prevents crop
material from entering beneath belt 32. Skid shoes 100, with
attached skid plates 102, move up and down on a localized basis
depending upon the ground terrain, and also concurrently carry the
leading edge of the return run of endless belt 32. Shields 118
extending from skid shoes 100 are positioned in front of the
leading edge of endless belt 32, and prevent material from
impinging upon or accumulating at the leading edge of the return
run of endless belt 32. The present invention therefore provides a
cutting platform which flexes to a high degree, efficiently moves
crop material to the feeder housing, and maximizes harvest yield by
better following the ground contour.
[0041] Having described the preferred embodiment, it will become
apparent that various modifications can be made without departing
from the scope of the invention as defined in the accompanying
claims.
* * * * *