Tractor and implement and hydraulic system therefor

A hydraulic system is provided for an integrally-mounted agricultural implement which permits control of the tractor three-point hitch rockshaft cylinder, upper draft link hydraulic cylinder and lift assist hydraulic cylinder through a single valve control lever. One end of the double-acting lift assist cylinder is plumbed in parallel with the single-acting rockshaft cylinder and the other end of the lift assist cylinder is plumbed in parallel with the single-acting upper link cylinder. The fluid lines are coupled with a single control valve to permit the implement to be supported by the lift assist wheel and three-point hitch during transport, permit it to rock about the lower connection with the three-point hitch during transport and float vertically at the hitch connection during field operations while operating with the lift assist wheel elevated.

BACKGROUND OF THE INVENTION 
The present invention relates generally to tractor and implement 
arrangements and more particularly to an improved hydraulic system for 
coordinating the action of a lift assist wheel on an integrally-mounted 
implement with the three-point hitch of the tractor. 
A significant amount of attention has recently been directed towards 
improving the productivity and profitability of farming operations. As a 
result, tractors with increased capacities and implements having wider 
toolbars capable of supporting greater weights are now commonly available. 
For agricultural operations which utilize tools such an cultivators or 
rotary hoes, it is common to integrally mount the implement toolbar to the 
three-point hitch of the tractor. During field operations, the weight of 
such an integrally-mounted implement is distributed through the tools to 
the ground and through the toolbar to the three-point hitch. However, when 
the tractor hitch and the integrally-mounted implement are elevated to 
permit transport of the implement, the weight is transferred totally to 
the rear of the tractor. Since tractors commonly available today are 
capable of pulling more than they can lift, integrally-mounted implements, 
if too wide and heavy will lighten the front of the tractor when they are 
lifted, possibly resulting in a complete loss of steering control. 
It is well known to provide larger integral implements with hydraulically 
actuated lift assist wheels to reduce the weight transferred to the 
tractor during transport. See, for example, the Model 7100 Mounted John 
Deere Planter. In such arrangements, actuation of the rockshaft hydraulic 
cylinder utilized to elevate the lower draft links of the three-point 
hitch is coordinated with the actuation of the lift assist hydraulic 
cylinder to raise and support the implement for transport. Typically, such 
an arrangement provides for the lift assist cylinder to be supplied with 
hydraulic fluid through lines coupled with a remote hydraulic cylinder 
outlet on the tractor while the rockshaft cylinder is supplied with 
hydraulic fluid through a separate hydraulic circuit contained within the 
housing of the tractor. Since each cylinder is supplied through a separate 
hydraulic circuit, at least two cab-mounted control levers must be 
manipulated to operate the cylinders. Accordingly, the operator must 
coordinate the two levers and actuation of the cylinders when raising the 
three-point hitch and lift assist wheel to transport the implement. 
Occasionally, structural damage can occur to either the hitch or implement 
when the actuation of the cylinders is not coordinated and the three-point 
hitch is not elevated in near synchronization with the lift assist wheel. 
A hydraulic circuit providing a single control lever to activate the 
tractor rockshaft cylinder and the implement lift assist cylinder has been 
provided when only single-acting lift assist cylinder capability is 
required. This ability is provided through special valving contained 
within a rockshaft piston cover available for John Deere Model 4030 and 
other similar tractors. The piston cover hydraulically connects the 
single-acting rockshaft cylinder in parallel with the lift assist 
cylinder. Accordingly, both cylinders are actuated when the rockshaft 
cylinder is pressurized and both cylinders are connected with the 
reservoir to permit them to be in a float configuration when the rockshaft 
hydraulic cylinder is not pressurized. 
This hydraulic circuitry permits the operator to extend the lift assist 
cylinder and lower the wheel for transport. However, during field 
operations, the rockshaft cylinder must be connected with the reservoir to 
allow the three-point hitch and implement to float vertically in response 
to ground contour changes. During this time, the lift assist wheel, which 
cannot be elevated since the lift assist cylinder is single acting, will 
travel along the ground behind the implement and compact the soil. If 
cultivating operations utilizing tools such as rotary hoes are performed, 
the trailing lift assist wheel will compact the soil loosened by the 
tools. Accordingly, it would be desirable to be able to elevate the lift 
assist wheel during such field operations. 
A double-acting hydraulic cylinder has been provided on integrally-mounted 
implements having trailing lift assist wheels, as for example, the John 
Deere Model 7100 Mounted Max-Emerge Planter. In this arrangement, the 
trailing lift assist wheel can be elevated during planting operations and 
lowered to assist during transport operations. However, the arrangement 
does not couple the lift assist cylinder with the rockshaft cylinder in a 
single hydraulic circuit utilizing a single control lever. Here also, the 
operator must synchronize two separate control levers to elevate the 
implement lift assist wheel and tractor three-point hitch for transport of 
the implement. 
A further problem which arises during transport of integral implements 
having trailing lift assist wheels occurs due to the changing ground 
contours and the lateral separation between the lift assist wheel and the 
implement connection with the tractor. As the lift assist wheel passes 
over ground contours different from those contours beneath the rear wheels 
of the tractor, the hitch connection will be put under compression or 
tension. To avoid structural damage to the hitch and/or implement during 
transport, some provision must be made to the connection to permit the 
implement to rock fore-and-aft about a transverse horizontal axis to 
accommodate the changing ground contours. 
The John Deere Model 7100 Mounted Max-Emerge Planter has provided a mast 
connection between the implement and a three-point hitch which permits the 
implement to rock fore-and-aft at its connection with the hitch. A 
single-acting hydraulic cylinder is coupled with the compression link of 
the three-point hitch and put into a float configuration during transport 
to enable the implement to rock. During field operations, the mast 
cylinder is pressurized to act as a rigid link and to enable the implement 
to float vertically over changing ground contours about the pivotal 
connection between the three-point hitch with the implement. While the 
7100 Mounted Planter with its hydraulic mast has provided a double-acting 
lift assist cylinder coupled with the single-acting mast cylinder, it does 
not provide a hydraulic system that also enables the operator to activate 
the single-acting rockshaft cylinder in near synchronization with the 
activation of the lift assist cylinder to avoid structural damage to the 
hitch and implement and to also simplify the operation of the 
integrally-mounted implement utilizing lift assist wheels. 
SUMMARY OF THE INVENTION 
To overcome these problems, a hydraulic system is provided which 
hydraulically couples a lift assist cylinder, a rockshaft cylinder and a 
compression link cylinder for activation through a single control valve 
and lever. To elevate the lift assist wheel during field operations yet 
lower it for transport, a double-acting lift assist cylinder is provided. 
To enable the implement to rock about a transverse horizontal axis during 
transport and yet remain rigid with the three-point hitch during field 
operations, a single-acting hydraulic cylinder is coupled with the 
compression link of the tractor three-point hitch. To allow the 
three-point hitch to float during field operations and the rockshaft 
cylinder to be unpressurized while the compression link cylinder is 
pressurized, the two cylinders are connected to separate sides of the 
fluid flow control valve. 
To elevate the double-acting lift assist cylinder during field operations 
and assure that the compression link cylinder is pressurized, the two 
cylinders are connected in parallel. To activate the rockshaft cylinder in 
near synchronization with the lowering of the lift assist wheel, the other 
end of the lift assist cylinder is connected in parallel with the 
rockshaft cylinder. To provide a single lever control for the three 
hydraulic cylinders, the two fluid lines connecting the compression link 
cylinder in parallel with one end of the lift assist cylinder and the 
other end of the lift assist cylinder in parallel with the rockshaft 
cylinder are coupled with a single remote cylinder outlet on the tractor 
and the rockshaft control valve is inactivated through providing either a 
valve or circuit disconnecting it from the rockshaft cylinder and 
connecting the rockshaft cylinder in parallel with the lift assist 
cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Looking now to FIG. 1, there is illustrated in side view a tractor 10 and 
an integrally-mounted implement 12 having a trailing lift assist wheel 14. 
The tractor 10 is of conventional construction and includes a main body 
carried on front steerable wheels (not shown) and rear tractor wheels 16. 
The rear portion of the tractor body is illustrated with one wheel removed 
and portions of the tractor housing broken away to reveal the various 
parts relevant to the invention. 
The tractor 10 includes a three-point hitch comprised of a pair of trailing 
lower draft links 18 and an upper compression link 20. The conventional 
upper link would generally include a turnbuckle but in the preferred 
embodiment is replaced with a single-acting hydraulic cylinder 22. Each 
link 18, 20 of the hitch is pivotally coupled with the tractor 10 at its 
forward end and is of such a length so as to permit a toolbar coupled with 
the rear connections of the links 18, 20 to shift in an essentially 
vertical plane as the links 18, 20 rock about their forward pivotal 
connections with the tractor 10. 
The tractor housing contains a single-acting rockshaft hydraulic cylinder 
24 having a rod 26 extending beyond the cylinder housing 28 and coupled 
with a transversely extending rockshaft 29 through lever 30. The rockshaft 
29 in turn carries at its opposite ends a pair of rearwardly extending 
lever arms 32 which are pivotally connected to respective draft links 18 
by drop links 34. When the single-acting rockshaft cylinder 24 is 
pressurized and the rod 26 is extended, the draft links 18 are raised. As 
hydraulic fluid is released from the rockshaft hydraulic cylinder 24 and 
the rod 26 is free to move, the draft links 18 are free to drop or rise 
with the implement as it follows the ground contour. 
At the rearward ends of the draft and compression links 18, 20 is carried 
an upstanding coupler element 36 for connecting implements 12 with the 
three-point hitch 38. The implement 12 includes a forwardly projecting 
mast structure 42 rigidly secured to the transversely extending toolbar 
44. The coupler 36 includes lower and upper supports 40 upon which the 
forwardly projecting mast structure 42 of the implement 12 can be quickly 
and easily secured to integrally mount it with the tractor 10. The toolbar 
44 further supports a plurality of rearwardly projecting earth-working 
tools 46. In the embodiment of FIG. 1, cultivator shovels 48 are 
illustrated although other earthworking tools can be and are commonly 
utilized with integrally-mounted implements. 
Rigidly connected to the toolbar 44 by U-bolts 50 is a rearwardly extending 
lift assist frame 52. The frame 52 carries at its trailing end a vertical 
member 54 upon whch a pair of vertically spaced generally parallel 
rearwardly extending links 56 are pivotally connected. The links 56 are 
pivotally attached at their rearward ends to a wheel support 58 which 
rotatably carries a lift assist wheel 60. Mounted between the upper link 
56 and the vertical member 54 is a double-acting hydraulic lift assist 
cylinder 62. While the preferred embodiment provides for the lift assist 
cylinder 62 to be positioned as illustrated, the invention could be 
practiced with the frame 52 being pivotally attached to the toolbar 44 and 
the cylinder 62 connected between the toolbar 44 and frame 52. 
The tractor 10 is provided with a conventional closed circuit hydraulic 
system having a source of hydraulic fluid pressure such as the reservoir 
64 and a variable displacement pump 66 as schematically illustrated in 
FIG. 3. A remote outlet servo valve, indicated generally by the numeral 
68, is carried within the tractor 10 and is connected to the reservoir 64 
by the fluid line 70 and to the pump 66 by fluid line 72. Leading from the 
valve 68 to a remote hydraulic cylinder outlet 73 are fluid lines 74 and 
76. A second servo valve 78 is conventionally provided in tractors for 
controlling the flow of fluid pressure to the rockshaft cylinder 24. Lines 
80 and 82 respectively connect that valve 78 with the reservoir 64 and 
pump 66. The valves 68 and 78 would be actuated through any suitable 
linkage, illustrated by dotted lines 84 and 86, by manually shiftable 
control levers 88 and 90 mounted on the tractor 10 near the operator. 
Fluid lines 92 and 94 are provided to couple the implement with the remote 
outlet 73 of the tractor 12. Each line 92 and 94, as well as the remote 
outlet 73, is provided with check valves to prevent fluid flow when 
disconnected. Line 92 connects in parallel the ram end of the 
single-acting link cylinder 22 with the ram end of the lift assist 
cylinder 62. Line 94 connects in parallel the base end of the lift assist 
cylinder 62 with the base end of the rockshaft cylinder 24. 
To deactivate the rockshaft control valve 78, a piston cover 102 is 
provided between fluid line 96, leading from the valve 78 and line 98 
leading to the rockshaft cylinder 24. The cover 102 connects the cylinder 
24 with either the valve 78 or valve 68 and when utilized with the 
invention inactivates valve 78, thereby providing the control for all 
three cylinders 22, 62 and 24 through valve 68. 
In the preferred embodiment, the piston cover 102 includes openings 106 and 
107 and a pressure relief valve 108. As illustrated in FIG. 2, fluid line 
110 is connected with fluid line 94 through the T-fitting 112 to couple 
the rockshaft hydraulic cylinder 24 in parallel with the base end of the 
lift assist cylinder 62. To disconnect the rockshaft cylinder 24 from 
fluid line 110 and reactivate the rockshaft valve 78, line 110 could be 
coupled with the outlet coupling 114 provided on the piston cover 102. 
Quick connect couplers are provided in line 110 and coupling 114 as well 
as the T-fitting 112. 
In operation, the piston cover 102 and hydraulic link cylinder 22 would be 
installed prior to connecting the implement 12 to the three-point hitch 
38. The piston cover 102 is installed by simply removing the bolts 116 
attaching the conventional cover to the piston and replacing it with the 
preferred cover 102. The hydraulic link cylinder 22 would then be 
installed after the compression link turnbuckle was removed. As 
illustrated in FIG. 3, the cylinder 22 would be provided with the 
T-coupling 118 to permit it to be connected in parallel with the ram end 
of the lift assist cylinder 62. 
The implement would then be connected with the three-point hitch coupler 
element 36 and the hydraulic lines 92 and 94 connected to the tractor 
remote outlet 73. The fluid line 94 connecting the lift assist cylinder 62 
with the piston cover 102 would be connected to the T-fitting 112 to 
connect the rockshaft cylinder 24 in parallel with the base end of the 
lift assist cylinder 62 and the T-fitting on line 92 would be connected to 
the hydraulic link cylinder 22 to connect the hydraulic link cylinder 22 
in parallel with the ram end of the lift assist cylinder 62. 
To transport the integral implement 12, the operator would shift lever 88 
to connect the pump 66 with lines 76 and 94 and the reservoir 64 with 
lines 74 and 92. The detent would maintain the valve 68 in that position 
until the operator again shifted it. As fluid flow pressurized line 98, 
the rockshaft rod 24 would extend lifting the links 18 and the ram of lift 
assist cylinder 62 would simultaneously extend lowering the wheel 60 into 
contact with the ground. As the drawbar links 18 would elevate the toolbar 
mast 42, the lift assist wheel 60 and frame 52 would elevate the toolbar 
44. As the pump pressurized line 94, the fluid in line 92 would flow from 
the rod end of the lift assist cylinder 62 to the reservoir 64 and fluid 
from the ram end of the single-acting hydraulic link cylinder 22 would be 
able to return to the reservoir 64, permitting the rod of cylinder 22 to 
float. During transport, the rockshaft cylinder 24 would be extended to 
maintain the three-point hitch 38 elevated, the lift assist cylinder 62 
would be extended to support the heavy integral implement 12 and the 
hydraulic link 22 would be able to float to permit the implement 12 to 
rock fore-and-aft about a horizontal axis through the pin connection 
between the mast 42 and coupler element 36. 
Once in the field, the operator would again shift the lever 88 to reverse 
the flow of fluid pressure in lines 92 and 94. As the valve 68 was shifted 
and fluid flows from line 94 to the reservoir 64, the rockshaft cylinder 
ram 26 would retract and the drawbar links 18 would lower. Simultaneously, 
as fluid flow pressurized line 92, the ram end of the lift assist cylinder 
62 would retract, elevating the list assist wheel 60 from the ground. The 
flow would also pressurize the hydraulic link cylinder 22 and cause the 
ram to retract and the cylinder 22 to act essentially as a rigid link. 
With the rockshaft cylinder 24 able to float, the three-point hitch 38 can 
shift vertically whenever the integral implement 12 encounters a change in 
ground contour requiring such movement relative to the tractor 10. With 
the lift assist cylinder ram retracted, the elevated lift assist wheel 60 
will not compact the soil recently worked by the tools 46. The retracted 
hydraulic link cylinder 22 will act as an essentially rigid link 
permitting the three-point hitch 38 to shift in an essentially vertical 
plane and about the pivotal connections between the drawbar links 18 and 
compression link 30 or cylinder 22 with the tractor 10. 
Thus the hydraulic system provided for the tractors utilizing 
integrally-mounted implements permits the operator to control the three 
cylinders 22, 62 and 24 through a single valve 68 and lever 88 and 
coordinate extension of the rockshaft cylinder 24 with extension of the 
lift assist cylinder 62 to elevate the implement 12 for transport without 
the possibility of incurring structural damage to the connections between 
the hitch 38 and implement 12.