Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND
An agricultural implement is typically connected to a tractor drawbar by a
clevis and
tongue connection. The Clovis provides upper and lower Clovis members each
defining a
draw pin hole, and the tongue defines a draw pin hole and is inserted between
the Bevis
members to align the draw pin holes such that a draw pin can be inserted
through them
and thereby connect the Clovis and tongue.
The clevis may be mounted to the tractor drawbar and the tongue provided by
the
Implement bitch, or vice versa. Essentially the tractor drawbar and the
implement hitch
are both "tongues', and the davis is provided by mounting a hammerstrap to the
tractor
drawbar or to the implement hitch. A harnmerstrap is simply a steel riser that
bolts to the
tongue adjacent to the draw pin hole and extends away from the tongue and then
along
the tongue and over the draw pia hole in the tongue. The draw pin hole in the
hanunerstrap is aligned with the draw pin hole in the tongue.
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The tractor drawbar supports the weight of the front end of the implement
being towed,
which can be considerable. Thus the tongue of the implement hitch must be
connected to
the drawbar so that the implement tongue rests on the drawbar. Thus where the
hammerstrap is mounted to the tractor drawbar, the hammerstrap is bolted to
the draw bar
forward of the draw pin hole in the drawbar, and then extends upward from the
drawbar
and then rearward over the draw pin hole in the drawbar. The implement hitch
rests on
the drawbar with the hammerstrap above it, and the draw pin is inserted down
through the
aligned draw pin holes in the hammerstrap, implement hitch, and drawbar.
Where the hammerstrap is mounted to the implement hitch, the hammerstrap is
bolted to
the hitch rearward of the draw pin hole in the hitch, and then extends
downward from the
hitch and then forward under the draw pin hole in the hitch. Again the
implement hitch
rests on the drawbar with the hammerstrap below the drawbar, and the draw pin
is
inserted down through the aligned draw pin holes in the implement hitch,
drawbar, and
hammerstrap.
Tractors come in a wide variety of sizes, and the draw pin hole in the drawbar
of each is
typically sized for a pin of sufficient strength to match the power of the
tractor.
Implements also come in a wide variety, and similarly have a hitch with a draw
pin hole
that is sized for a pin of sufficient strength to match the power requirement
of the
implement.
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It is desirable to have the draw pin hole all the same size so that a
corresponding size of
draw pin can be inserted to connect the clevis and tongue in the preferred
manner such
that there is only minimal movement at the connection. Another consideration
is the
need for articulation at the connection between the tractor and implement to
allow for the
required relative movement between them. The draw pin provides a vertical axis
so that
the implement and tractor can pivot widely with respect to each other about
the vertical
axis during turns. Since these implements are towed over uneven terrain the
implement
and tractor must also be allowed at least some pivotal movement about a
horizontal axis
oriented perpendicular to the operating travel direction, and about a
horizontal axis
aligned with the operating travel direction. This articulation is commonly
provided by
lengthening the draw pin hole in the tongue, and making the tongue draw pin
hole
somewhat wider than the draw pin, so that the draw pin can angle forward or
rearward,
and laterally in the draw pin hole in the tongue.
The predominant area of wear on an implement hitch is the front surface of the
draw pin
hole. It is this surface against which the draw pin bears when pulling the
implement in
the operating travel direction, where full load is placed on the draw pin.
Also the bottom
of the implement hitch tongue rests on the tractor drawbar with considerable
downward
force, and as the tractor and implement turn and pivot about the vertical draw
pin, the
bottom of the implement hitch tongue wears against the top of the tractor
drawbar. Thus
it is common to make the tongue of the implement hitch out of hardened steel
to resist
this wear, and prolong the useful life of the hitch tongue.
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SUMMARY OF THE INVENTION
It is an object of the present invention to provide an implement hitch
apparatus that
overcomes problems in the prior art.
The implement hitch apparatus of the present invention provides right and left
side plates
with mounting holes defined therein and configured to attach to corresponding
right and
left hitch mounting members at the front end of an implement such that the
side plates are
oriented substantially vertically. The right and left side plates also define
right and left
lug apertures. A middle hitch plate defines a middle draw pin hole extending
substantially
vertically through a front portion thereof, and right and left lugs extending
from
corresponding right and left edges of a rear portion thereof through
corresponding right
and left lug aperture in the side plates.
Upper and lower hitch plates are fastened to corresponding upper and lower
surfaces of
the middle hitch plate. The upper and lower hitch plates define corresponding
upper and
lower draw pin holes extending substantially vertically through front portions
thereof
such that front edges of the upper, middle, and lower draw pin holes are
vertically
aligned. Right and left lugs extend from corresponding right and left edges of
rear
portions of the upper and lower hitch plates through the corresponding right
and left lug
apertures in the side plates.
Thus a draw pin extending through the aligned upper, middle, and lower draw
pin holes
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S
bears against all three plates. The force in the operating travel direction
exerted by the
draw pin on all of the hitch plates is transferred through all of the lugs to
the side plates
and through the bolts mounting the side plates to the hitch mounting members
at the front
end of the implement. The plates will typically be fastened together by
welding however
the strength of the hitch apparatus does not depend on these welds. The plates
are
typically laser cut to provide the lugs which bear the draft forces of the
implement. The
thickness of the three hitch plates is coordinated to provide the required
strength for a
given implement.
The three plate design also allows the upper and lower draw pin hole to be
somewhat
wider and longer than the middle draw pin hole. The upper and lower draw pin
holes
thus provide added empty space to allow for articulation and angling of the
draw pin
when in the draw pin holes, while the smaller middle draw pin hole desirably
minimizes
movement at the connection.
Further the upper and lower hitch plates can be made of hardened steel to
reduce wear on
the front edge of the upper and lower draw pin holes. The middle hitch plate
can be
made from cheaper mild steel, since the front edge of the middle draw pin hole
will be
protected from wear by the hardened upper and lower hitch plates. The hardened
lower
hitch plate rests on the tractor drawbar and will reduce wear in that area. A
clevis
attachment can also be provided.
DESCRIPTION OF THE DRAWINGS
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While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a top view of an embodiment of an implement hitch apparatus of the
present
invention;
Fig. 2 is a side view of the embodiment of Fig. 1 with the facing side plate
removed to
facilitate illustration;
Fig. 3 is a top view of the middle hitch plate of the embodiment of Fig. 1;
Fig. 4 is a side view of the middle side plate shown in Fig. 3;
Fig. 5 is a top view of the part that provides both the upper and lower hitch
plates of
the embodiment of Fig. 1;
Fig. 6 is a side view of the upper and lower hitch plate shown in Fig. 5;
Fig. 7 is a top view of a side plate of the embodiment of fig. 1;
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Fig. 8 is a side view of the side plate shown in Fig. 7 shown adjacent to the
hitch
mounting members of an implement to hitch the apparatus is to be attached;
Fig. 9 is a schematic side view of the embodiment of Fig. 1 showing fore and
aft
articulation of a draw pin;
Fig. 10 is a schematic sectional view of a prior art cast implement hitch;
Fig. 11 is a side view of an alternate embodiment of the implement hitch
apparatus of
the present invention including a hammerstrap mounted in a first orientation
with the
end A of the apparatus up and end B of the apparatus down;
Fig_ 12 is a side view of the alternate embodiment of Fig. 11 mounted in a
second
orientation with the end A of the apparatus down and end B of the apparatus up
to
accommodate a tractor drawbar that is an increased height above the ground.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Figs. 1-8 illustrate an implement hitch apparatus 1 of the present invention.
The
apparatus 1 provides right and left side plates 3 with mounting holes 5
defined therein.
The mounting holes 5 are configured to attach to corresponding right and left
hitch
mounting members 7 at the front end of an implement such that the side plates
3 are
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oriented substantially vertically. The right and left side plates 3 also
define right and left
lug apertures 9.
A middle hitch plate 17M, as illustrated in Figs 3 and 4 defines a muddle draw
pin hole
13M extending substantially vertically through a front portion thereof Right
and left
lugs -15 extend from corresponding right and left edges of a rear portion of
the middle
hitch plate 17M and through the corresponding lug apertures 9 in the right and
left side
plates 3.
Upper and lower hitch plates 17U, 17L are fastened to corresponding upper and
lower
surfaces of the middle hitch plate 17M. The upper and lower hitch plates 17
are the same
item illustrated in Figs. 5 and 6. The upper and lower hitch plates 17U, 17L
define
corresponding upper and lower draw pin holes 13U, 13L extending substantially
vertically through front portions thereof. As seen in Fig. 2, front edges 19
of the upper,
middle, and lower draw pin holes 13U, 13M, 13L, are vertically aligned. Right
and left
lugs 15 extend from corresponding right and left edges of rear portions of the
upper and
lower hitch plates 17 through the corresponding lug apertures 9 in the right
and left side
plates 3.
A draw pin extending through the aligned upper, middle, and lower draw pin
holes 13U,
13M, 13L will bear against all three plates 17M, 17U 17L. The force in the
operating
travel direction T exerted by the draw pin on the hitch plates is transferred
through the
lugs 15 to the side plates 3 and through the bolts mounting the side plates 3
to the hitch
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mounting members 7 at the front end of the implement. The plates 17M, 17U 17L
will
typically be fastened together by welding however the strength of the hitch
apparatus
does not depend on these welds but rather on the lugs 15 on each plate which
bear the
draft forces of the implement. The plates 17M, 17U 17L are typically laser cut
to
provide the lugs 15, and the thickness of the three hitch plates is
coordinated to provide
the required strength for a given implement.
The three plate design also allows the upper and lower draw pin holes 13U, 13L
to be
somewhat wider and longer than the middle draw pin hole 13M. As seen in Figs.
3 and
5, only the front edges 19 of the draw pin holes 13U, 13M, 13L are shaped the
same, such
that a cylindrical draw pin will bear against the front edge of each hole as
shown in pig.
1. Rearward of the front edges 19, it can be seen that the upper and lower
draw pin holes
13U, 13L have a width W' that is greater than the width W of the middle draw
pin hole
13M. The upper and lower draw pin holes 13U, 13L also include a recess 21
extending
rearward such that they are also longer than the middle draw pin hole 13M.
The upper and lower draw pin holes I3U, 13L thus provide added empty space
above and
below the edges of the middle draw pin hole 13M to allow for articulation and
angling of
the draw pin 23 when in the draw pin hole 13 formed by the upper, middle, and
lower
draw pin holes 13U, 13M, 13L as illustrated in Fig. 9.
The smaller middle draw pin hole 13M desirably minimizes movement at the
connection
when the implement is being moved in reverse for example or in other non field
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operating conditions. When the implement is subject to the full draft forces
in the field
operating position it will be moving in the operating travel direction T and
the draw pin
will bear against the front edges of all the draw pin holes 13U, 13M, 13L, but
when
articulation is required the pin can move from position PA indicated by the
solid lines
5 shown in Fig. 9, to position PB indicated by the long dashed lines shown in
Fig. 9. When
fore and aft articulation downward of the tractor with respect to the
implement is required
the draw pin 23 pivots about pivot point PP the top of the front edge 19 of
the upper draw
pin hole 13U and the bottom of the draw pin 23 moves rearward into the recess
21 in the
lower hitch plate I7L. An articulation angle N is thus available in the
illustrated
10 implement hitch apparatus 1.
In contrast if the recess 21 was not provided, the rear edges of the middle
and lower draw
pin holes would be aligned, and the draw pin 23 would only be able to move to
position
PC and the articulation angle available would be reduced to angle N'.
Similarly
increased lateral. articulation is accommodated by the added width of the
upper and lower
draw pinhole 13U, 13L.
The present invention thus provides an implement hitch apparatus that is
economically
manufactured by present day laser cutting techniques. It is common in prior
art hitches,
such as the implement hitch 101 schematically illustrated in Fig. 10, to
provide a cast
hitch member 117 that defines a draw pin hole with round edges 119 all around
the draw
pin hole 113 that accommodate articulation. The present invention does not
require
costly molds and tooling for each different size and configuration of hitch
required, and
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so is readily adapted to a variety of implements. The side plates 3 and hitch
plates 17M,
17U, 17L can be cut in any shape and quantity that is desired.
A further advantage of the present invention is that the upper and lower hitch
plates 17U,
17L can be made of hardened steel to reduce wear on the front edge 19 of the
upper and
lower draw pin holes 13U, 13L. The middle hitch plate 17M can be made from
cheaper
mild steel, since the front edge 19 of the middle draw pin hole 13M will be
protected
from wean by the hardened upper and lower hitch plates 17U, 17L. Also, the
hardened
lower hitch plate 17L rests on the tractor drawbar and will reduce wear in
that area. In
the prior art hitch 101 of Fig. 10, the entire cast hitch member 117 was made
of costly
hardened material.
It can be seen as well that in the illustrated apparatus 1, the upper and
lower hitch plates
17U, 17L are somewhat narrower and shorter than the middle hitch plate 17M.
Thus the
more costly hardened upper and lower hitch plates 17U, 17L are smaller and
require less
of the expensive hardened material. The middle plate extends farther rearward
between
the right and left side plates 3 and is welded between the plates 3 to
stabilize the
apparatus 1. Also a ledge 25 is provided that is convenient for fillet welding
the middle
hitch plate 17M to the upper and lower hitch plates 17U, 17L.
Figs. 1 I and 12 illustrate an alternate embodiment of the implement hitch
apparatus 201
of the present invention. The side plates 203 are of a somewhat different
design that is
common for heavier implements where the upper, middle, and lower hitch plates
form a
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hitch member 217 with lugs 215 extending through lug apertures 209 located in
a bottom
portion of the side plates 203 and the side plates are attached to the hitch
mounting
members 207 by three bolts. A hammerstrap 231 is attachable with bolts 233 to
either
side of the hitch member 217, as shown by phantom lines in Fig. 11, to allow
the
implement hitch apparatus to be mounted to the hitch mounting members 207 with
either
side up, and still maintain the hammerstrap 231 under the bitch member 217 so
that the
hitch member 217 rests on the tractor drawbar 235.
Thus where the drawbar 235 is a lower height H above the ground as shown in
Fig. 11,
the implement hitch apparatus 201 is mounted to the hitch mounting members 207
with
end A up and end B down. Where the drawbar 235 is a greater height H' above
the
ground as shown in Fig. 1, 2, the hammerstrap is mounted on the opposite side
of the hitch
member 217 and the implement hitch apparatus 201 is reversed and mounted with
end A
down and end B up.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
