Height control system with multiple control valves

Height sensing structure utilizing a pair of height sensing valves connected to height sensing shoes on two row harvesting units. The row harvesting units are transversely adjustable on support structure to accommodate different row spacings and to open up space between the units for service and inspection. The height control valves are connected by flexible conduit and a shuttle check valve to a lift cylinder, and interconnecting linkages between the height sensing shoes on adjacent units are eliminated so that the units may be freely adjusted. The shuttle valve assures that the height control valve sensing the highest ground condition controls the lift cylinder to prevent "digging in".

BACKGROUND OF THE INVENTION 
The present invention relates generally to agricultural implements, and 
more specifically to height control structure for automatically 
controlling the location of a portion of the implement relative to the 
ground. 
On agricultural equipment, such as a cotton picker, more than one 
harvesting unit or the like is raised and lowered by a single lift 
structure, and height sensing is typically accomplished with a single 
valve attached to one of the units. A mechanical linkage, extending 
transversely between units, links a height-sensing shoe from each unit to 
the single valve. The valve, in turn, is connected to a hydraulic cylinder 
which raises and lowers the unit support structure in response to movement 
of the shoes. The linkages are generally bulky and joints tend to wear and 
cause lost motion which affects the operation and adjustment of the height 
control system. The connections between unit hinder lateral movement of 
the units for row spacing adjustment and for access to the row units for 
service. If a single height-sensing shoe is utilized to eliminate the 
linkage between units, the units which are offset from the height-sensed 
unit are susceptible to "digging in" in rough or irregular terrain. 
In co-pending application, Ser. No. 087,073, filed Aug. 19, 1987 of Steve 
Allan Junge and Timothy Arthur Deutsch and commonly assigned with the 
present application, picking unit support structure is disclosed which 
provides easy lateral adjustment of row units on a support frame for 
quickly changing row spacings or for opening up areas between units for 
inspection and servicing. Mechanical linkages between height-sensing shoes 
on different units can reduce the flexibility, adjustability and 
serviceability of such a structure. However, it is necessary to provide 
more than one height sensing member in order to eliminate problems of 
digging in at one of the structure, particularly when up to three 
harvesting units may be supported on a single frame. 
BRIEF DESCRIPTION OF THE INVENTION 
It is therefore an object of the present invention to provide improved 
height sensing structure for an agricultural implement. It is a further 
object to provide such structure which has fewer and shorter mechanical 
linkages than at least most previously available height sensing 
structures. 
It is yet another object of the present invention to provide an improved 
height sensing structure having at least two height sensing members spaced 
from each other on different units on the implement. It is still another 
object to provide such structure which provides improved flexibility, and 
facilitates lateral adjustments of the units for such things as servicing 
of the units and accommodating different row spacings. It is another 
object to provide such a structure which eliminates mechanical linkages 
extending between the height sensing members. 
It is yet another object of the invention to provide an improved height 
sensing structure including at least two height sensing members spaced on 
an implement and connected by a hydraulic circuit which eliminates 
mechanical linkages and provides reliable height sensing to avoid digging 
in. 
In accordance with the above objects, height sensing structure is provided 
having two height control valves mounted closely to two height sensing 
shoes on transversely spaced and adjustable harvesting units. Each valve 
is actuated by the corresponding height sensing shoe. The shoes are not 
mechanically linked together so that long cumbersome linkages which would 
otherwise limit flexibility and increase sensitivity and adjustment 
problems are eliminated. A shuttle check valve is connected to the outputs 
of the two valves and prevents one valve from overriding the other and 
causing a unit to operate too low to the ground. The shuttle valve causes 
the unit sensing the highest ground to control the height of all the units 
and prevent digging in. Flexible hoses are utilized to connect to the 
valves so that the units may be easily adjusted with respect to each other 
and so that access and service areas are not blocked by any of the height 
sensing structure. 
These and other objects, features and advantages of the present invention 
will become apparent to those skilled in the art from the description 
which follows and from the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a cotton harvester 10 having a main 
frame 12 supported for forward movement over the ground by ground wheels 
14. A plurality of transversely spaced row units 16 are carried on 
vertically adjustable support structures 18 which extend in the transverse 
direction ahead of the respective wheels 14. As shown, the row units and 
support structures are of the type shown and described in the 
aformentioned Junge and Deutsch application, and the units are easily 
rolled laterally to adjust for differing row widths and to open up the 
area between the units for service and inspection. Each support structure 
18 is connected by lift structure 22 (FIG. 2) to the harvester frame 12, 
and a hydraulic cylinder 24 connected between the frame 12 and the support 
structure 18 is operable to raise and lower the support structure 18 to 
maintain the row units 16 at the proper height for harvesting crop from 
the rows of plants. Height sensing structure 30 is connected to the row 
units 16 and to the lift cylinder 24 to automatically maintain the support 
structure 18 at the proper height above the ground. The height sensing 
structure 30 includes two height sensing shoes or skids 32 and 34 
transversely offset from each other on the support structure 18. 
Preferably, the shoes 32 and 34 are supported in a conventional manner 
from a lower portion of stock lifters 36 connected to the forward portion 
of the row unit 16. The shoes 32 and 34 are substantially identical and so 
only the shoe 32 will be described in detail. The shoe 32 is pivotally 
connected at 42 and extends downwardly and rearwardly therefrom to an 
upwardly directed rear portion 44. An adjustable length link 46 is 
connected rearwardly adjacent the pivotal connection 42 for movement with 
the shoe 32 with variations in the distance between the row unit and the 
surface of the ground. 
A height sensing valve 52 is supported by the stock lifter 36 closely 
adjacent the shoe 32 and includes a spool operably connected to the shoe 
by the adjustable length link 46. The valve 52 is a three position three 
port valve having inputs 56 and 58 (FIG. 3) and an output 62. The valve 52 
has a "lower" position wherein the input port 56 is blocked and the input 
port 58 is in communication with the output port 62. The spool is movable 
to a second or "neutral" position wherein the ports 56, 58 and 62 are 
blocked. The spool is movable upwardly from the neutral position to a 
"raise" position wherein the port 56 is in communication with the output 
port 62 and the port 58 is blocked. An identical height sensing valve 54 
is operably connected to the shoe 34. 
The input ports 56 for the valves 52 and 54 are connected together and to a 
source or pressure through a one-way check valve 68. The input ports 58 
are also connected together and are connected to a three position operator 
control valve 72 through a pilot operated check valve 74. 
A shuttle valve 82 includes input ports 84 and 86 connected to the output 
ports 62 of the respective valves 52 and 54. The shuttle valve 82 also 
includes an output port 88 connected to the base end of the cylinder 24. 
Pressurized hydraulic fluid at the input ports 84 and 86 will act on 
opposite sides of a floating ball 92 to automatically connect the output 
port 88 with the input port having the highest pressure. The input port 86 
of the shuttle valve 82 is also connected through a one-way check valve 94 
to the check valve 74 at the output of the operator control valve 72. 
The hydraulic circuit includes flexible hoses indicated generally at 98 
connecting the valves 52, 54 and 82 to permit the row units 16 to be 
adjusted freely with respect to each other without hindrance from the 
height sensing structure. The conduits connecting the various valves are 
routed along the row units to provide unhindered access to the units for 
servicing and inspection. 
In operation, assuming that the lift cylinder 24 is fully extended so that 
the support structure 18 with the row units 16 is lifted above the ground 
in a transport position, the height sensing shoes 32 and 34 will be 
pivoted downwardly so that the spools of the valves 52 and 54 will be in 
their "lower" positions as shown in FIG. 3. To move the row units 16 
downwardly to a position within the range of the height sensing structure 
30, the operator moves the control valve 72 from the neutral position (as 
shown in FIG. 3) to the right to open the check valve 74 and thereby open 
the input ports 58 to reservoir. Fluid will be forced out of the base end 
of the lift cylinder 24 through the shuttle valve 82, the valves 52 and 54 
and the check valve 74 to reservoir. The row units 16 will move downwardly 
with the support structure 18 until, assuming level ground conditions, 
both of the valves 52 and 54 are moved to their "neutral" positions 
wherein the ports 56, 58 and 62 are closed and fluid is prevented from 
moving out from the cylinder 24. If a one of the units 16 moves downwardly 
below a preselected height above the ground, the corresponding valve will 
be moved to the "raise" position wherein the high pressure input port 56 
is in open communication with the output port 62 of the same valve, and 
fluid under pressure will be communicated from the output port 62 through 
the shuttle valve 82 to the lift cylinder 24 to raise the support 
structure 18 and lift the row units 16 until both height sensing valves 
are moved away from the "raise" position. The shuttle valve 82 
communicates the highest pressure at the input ports 84 and 86 to the lift 
cylinder 24 to assure that the row unit 16 sensing the highest ground 
level controls the heights of all the row units 16 on the support 
structure 18 to prevent digging in. 
To raise the support structure 18 and corresponding row units 16 from the 
height control range to a raised transport condition, the operator moves 
the control valve 72 to the far left (FIG. 3) to open the check valve 74 
and pressurize the input line connected to the input ports 56 and 58. The 
check valve 94 permits fluid under pressure to flow freely around the 
valves 52 and 54 through the shuttle valve 82 into the base of the 
cylinder 24 to extend the cylinder and raise the units to the transport 
position. The operator may also maintain the support structure 18 in a 
preselected minimum height position by moving the operator control valve 
72 to the position shown in FIG. 3 once the support structure 18 is at the 
desired height. When the valve is in the central or neutral position, the 
check valve 74 is closed preventing flow of hydraulic fluid from the base 
end of the cylinder 24 regardless of the positions of the spools in the 
height sensing valves 52 and 54. However, if either of the height sensed 
row units 16 begins to operate too low to the ground, the corresponding 
height sensing valve will move to the "raise" position and fluid under 
pressure will be communicated through the check valve 68 and the height 
sensing valve through the shuttle valve 82 to the cylinder 24 to cause the 
cylinder to extend and move the row units upwardly until the spool of the 
height sensing valve moves to the neutral position. 
Having described the preferred embodiment, it will be apparent that 
modifications can be made without departing from the scope of the 
invention as defined in the accompanying claims.