Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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THREE-POINT HITCH ASSEMBLY
BACKGROUND OF THE INVENTION
This invention relates to a three-point hitch
assembly particularly of the type which can be attached
to the conventional drawbar of an older type tractor
which has not been equipped with a three-point hitch.
Various proposals have been made for a device
of this type but a requirement remains for a simple
rugged construction which has the properties of enabling
the lower draft arms of the three-point hitch to be
raised by hydraulic cylinders, for -the lower draft arms
to be locked in ~he raised position or for them to be
free to float above the raised position. It will be
appreciated that some implements require the three-point
hitch to be effectively fixed at a desired height and
yet ot'ner implements require some floating action so
that if the implement hits an obstacle it can lift or
float over t'ne obstacle by lifting away from the other-
wise fixed position of the hydraulic lifting mechanism.
20 `~` It is a Eurther important requirement of a
device of this type that the two arms be lifted at the
same rate of movement despite different loads being
applied to the arms by the implement.
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SUMMARY OF THE INVENTION
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It is a first object of the invention there-
fore to provide a three-point hitch device which is of
simple, rugged and effective construction and which
provides the alternative of the lower draft arms being
fixed or locked in position, or alternatively free to
float above the position.
Accordingly~ the invention provides a three-
point hi-tch assembly for attachment to a tractor com-
prising a pair of lower draft arms for extending rear-
wardly of the tractor, frame means for attachment to
the tractor and for supporting said lower draft arms
for pivotal movement about a first horizontal axis, a
pair of lift arms mounted on the frame for pivotal move-
ment about a second horizontal axis above said first
axis, a pair of connecting links each for connecting a
respective lift arm to a respective lower draft arm, a
pair of hydraulic cylinder and piston devices each con-
necting between the frame and the respective lift arm
whereby the lift arms can be raised and lowere~ by ope-
ration of the hydraulic cylinders to raise and lower the
lower draft arMs, loose coupling means between each cy-
linder and piston device and the respective lift arm to
allow floating movement of the lower draft arms and
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the
means for locking/loose coupling means to prevent said
floating r,lovement.
It is a particularly advantageous feature of
the i.nvention that the loose coupling means comprises
a lever pivotally connected to the lift arm and to the
cylinder and pis~on device and means for limiting pivot-
al movement of the lever relative to the lift arm.
It is a further advantageous feature of t'ne
invention that the lift arm comprises a channel section
member with the lever mounted within the channel sec-
tion for pivotal movement about a transverse axis out of
the channel section, and a channel guide connected to
the channel section so the movement of the lever is de-
limited by engagement with the channel section and with
a closed end of the channel guide.
In accordance with a yet further important
feature of the inven.ion there is provided first fluid
connection means for connecting pressurized hydraulic
fluid from a supply to an expansion side of the piston
of one of the cylinders, second fluid connection means
for connection of the fluid from the retraction side of
the piston of said one cylinder to the expansion side
of the piston of the other cylinder and third fluid con-
nection means for connecting fluid from the retraction
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side of the piston o the other cylinder for return to
the supply, said one cylinder and piston being greater
in diameter than said other whereby the swept volume on
the retraction side of said one is equal to the swept
volume on the expansion side of said other whereby the
cylinders operate in series at the same rate of move-
ment.
With the foregoing in view, and other advan-
tages as will become apparent to those skilled in the
art to which this invention relates as this specifica-
tiuon proceeds, the invention is herein described by
reference to the accompanying drawings forming a part
hereof, which includes a description of the best mode
known to the applicant and of the preferred typical em-
bodiment of the principles of the present invention,
in which:
DESCRIPTION OF THE FIGURES
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Figure 1 is a cross sectional view of the
hitch assembly in a locked position, the cross section
taken along lines 1-1 of Figure 3.
Figure 2 is a side elevational view similar
to that of Figure 1 showing the assembly in a floating
position.
Figure 3 is a front elevational view of the
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assembly of Figure 1.
Figure 4 is a top plan view of the assembly of
Figure 1.
In the drawings like characters of reference
indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
The hitch assembly for attachment to the con-
ventional drawbar of a tractor comprises a support frame
generally indicated at 10 including a lower angle iron
section 11, an upper angle iron section 12 and two sup-
port legs 13, 14 thus forming a rectangular frame which
can sit on the drawbar of the tractor. A pair of pads
15 are welded to the underside of the lower angle iron
- 11 in order to rest upon the drawbar of the tractor.
The legs 13~ 14 are formed of square section tubing
and are welded to the angle iron sections 11 and 12 to
form a rigid structure.
Within the upper angle iron section 12 at the
top of the legs 13, 14 respectively is welded a pair
of collars 16, 17 for rotatably supporting a shaft 18
in the form of a pipe which extends along the full
length of the section 12 and beyond the ends to a posi-
tion beyond the collars 16, 17. Centrally of the upper
section 12 is provided a third collar 19 which again sup-
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ports the shaft 18 and also receives a bracket 20 which
can be attached to the upper control arm of the three-
point hitch in a conventional manner.
Rearwardly of the frame at the bottom section
11 and adjacent the legs 13~ 14 is positioned a pair of
flanges 21, 22. The flanges extend rearwardly from the
frame and provide a pivotal support by way of a bolt 23
for a pair of lower lift arms 24, 25 which extend from
the flanges 21, 22 forwardly beyond the frame 10 to a
forwardly extending coupling member 26 for attachment
to an implement in a conventional manner. Thus, the
arms 24, 25 together with the upper support arm attached
to the coupling 20 provide the three-point hitch arrange-
ment which can pivot upwardly and downwardly relative
to the pivot pins 23 and also the coupling 20.
To accommodate sideways movement of the lower
lift arms 24, 25 a pair of plates 27, 28 are provided
which lie inwardly of the arms 24~ 25 either in contact
therewith or slightly spaced therefrom so that as the
arms 24, 25 pivot upwardly, they slide against the plates
27, 28 thus inhibiting sideways or lateral movement of
the arms 24, 25. The plates 27, 28 are mounted upon the
outer side of the legs 13, 14 by way of a welded plate
29 and a pair of bolts 30 which include spacers to set
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the position of the plates 27, 28 re].ative to the arms
24, 25.
The shaft 18 supports a lift assembly for the
lower lift arms 24, 25 generally indicated at 31. The
lift assembly comprises a pair of outer arms 32~ 33 which
extend from the shaft 18 forwardly to a position parallel
to and above the lift arms 24, 25. The outer arms 323
33 are coupled to the lower lift arms 24, 25 respectively
by a pair of linkages 34. The lower end of the linkage
34 includes a bifurcated support 35 for receiving a
transverse pin 36 which passes through an opening 37 in
the upper edge of the lift arm~ The length of the link-
age is adjustable by a male and female co-operating screw
thread 38 with the upper end of the male screw thread
being attached to a furth~r bifurcated link 39 coupled
in turn to a flange 40 of the upper outer arms 32, 33 by
a pin 41. The arms 32, 33 are of square cross sectioned
tubing and the flange 40 is formed in a slot along the
length of the tubing and welded to the tubing so as to
extend downwardly beneath the arm for receiving the pin
41.
The linkage 34 therefore, acts to communicate
movement of the outer arms 32, 33 to the lower lift arms
24, 25 with the screw thread 38 providing adjustment o
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the angle between the arms 32, 33 and the lower lift
arms 24, 25. As shown in Figure 1, the arms are arran-
ged parallel but this can be adjusted in order to lift
or lower the coupling 26 while maintaining the arm 33
stationary.
The lift assembly 31 also includes a second pair
pair of arms 42, 43 parallel to the outer arms and posi-
tioned inwardly thereof. It will be noted that the col-
lars 16, 17 are positioned respectively so that the out-
er arm lies on one side of the collar and the inner armlies on the other side of the collar with the collar sub-
stantially filling the space therebetween. The length
of the arms 42, 43 is less than the respective outer
arms 32, 33.
A coupling bar 44 is welded to the outer end
of the arms 32, 42 and 33, 43 so as to provide a rigid
coupling therebetween which coop~rates with the rigidity
of the shaft 18 so that the inner and outer arms co-
rotate about the axis of the shaft 18. In addition, as
a further supporting bracket, a gusset 45 is connected
between the arms 42, 43 and the shaft 18, so that the
shaft, arms 42, 43 and arms 32, 33 comprise a rigid as-
sembly which together rotates around the axis of the
shaft 18.
The arms 42, 43 are again formed from square
section tubing but include a transverse opening 46
for receiving a pivot pin ~7 of a lever ~8. In addition,
the lowermost face of the s~uare section tubing of
the arm is cut away at a position forwardly of the pivot
pin 47 to allow a flange 49 of the lever 48 to project
downwardly out of the tubing of the arm. Furthermore,
beyond the cut away section indicated at 50, the lower
edge of the tubing is extended by an extension portion
51 oE the same width as the tubing to provide a slideway
for the end of the lever 48 so that this can move up-
wardly and downwardly from a raised position where it
is received wholly within the tubing of the arm 43 to
a lowered position where it is received within the ex-
tension portion 51.
These positions are illustrated respectively
in Figures 1 and 2.
In order to latch the lever 48 in the upper
position illustrated in Figure 1, an opening 52 is pro-
vided at the junction between the tubing and the exten-
sion portion 51 so that a pin 53 can be inserted be-
neath the lower surface of the lever.
The flange 49 of the lever 48 is attached by
a bifurcated coupling 54 to a piston rod 55 of a cylin-
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der 56. The other end of the cylinder is attached again
by a bifurcated coupling 57 to a lug 58 on the angle
iron 11 using a pivot pin 59.
Turning to Figure 3 particularly, it will be
noted that there are two cylinders 56, the left hand one
of which is indicated at 561 and the right hand one of
which is indicated at 562. The cylinders are arranged
in respective vertical planes and extending from a posi-
tion within the frame 10 to a position at the end of the
piston rod slightly forwardly of the frame 10 so that
by extension of the piston within the cylinder 56, the
lever 48 can be raised thus raising the arms ~2, 43.
Observing the hydraulic linkage to the cylin-
ders 62, 562 it will be noted that they are ranged in
series rather than in parallel. Thus, fluid supply
from a pump 60 is connected to the extension side of the
piston indicated at 62 of the cylinder 562 and thus acts
to expel the cylinder to extend the piston rod to lift
the lever 48. The fluid expelled from the downstream
side of the piston 62 is communicated via a duct 63 to
the expansion side of the piston 64 of the cylinder 561.
Fluid ejected by movement of the piston 64 is
connected to a sump schematically indicated at 61 rom
a cylinder 561. It will be noted furthermore that the
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diameter of the cy].inder 562 is greater than that of the
cylinder 561 so that the volume of fluid swept by the
upper side of the piston 62 is equal to the volume of
fluid causing movement of the piston 64. The differ-
ences in diameter therefore accommodates the piston rod
55 of the piston 62 which takes up some of the volume
above the piston 62.
Thus, coupling the cylinder in series as oppo-
sed to in parallel ensures that the arms 42, 43 are lift-
ed at the sa~e ratè. regardless of any difference of loadapplied thereto.
It will be apparent that lifting of the arms
42, 43 via the levers 48 will also cause lifting move-
- ment of the arms 32, 33 and therefore the lower lift
arms 24, 25.
In a locked position of the lever 48 as shown
in Figure 1, the arms ?4, 25 are effec~ively rigidly
coupled to the piston rods 55 and therefore are locked
in position by the hydraulic cylinders 56. Thus, they
can be raised to a required position and then retained
in that position and cannot raise from that positionO
However, in the position illustrated in Figure
~ where the pin 53 is removed thus releasing the lever
48, the arms 43 can lift relative to the lever 48 un-
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der force from the arms 24, 25. The degree of lifting
or floating movement is controlled by the portion 51 of
the arms 42, 43 but within the limits of that control
the arms 24, 25 and therefore the couplings 26 can lift
up and down without adjustment of the cylinders 56. Such
floating action is required in relation to equipment
which needs to lift over uneven t~rrain but to return
to the required adjusted position as soon as the uneven
terrain is passed.
Since various modifications can be made in my
invention as hereinabove described, and manay apparent-
ly widely different embodiments of same made within the
spirit and scope of the claims without departing from
such spirit and scope, it is intended that all matter
contained in the accompanying specification shall be
interpreted as illustrative only and not in a limiting
sense.
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