GB2340724A

GB2340724A - Hitch assembly

Info

Publication number: GB2340724A
Application number: GB9916178A
Authority: GB
Inventors: Jeffrey A Moore; Lynn A Sutton
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 1998-08-24
Filing date: 1999-07-09
Publication date: 2000-03-01
Also published as: AU4110999A; GB9916178D0

Abstract

The present invention provides a hitch assembly that includes a pair of draft arms 20,22 that are pivotally mounted between the machine frame 12 and the implement (not shown). Each draft arm is independently pivoted about its mounting by a lift cylinder 44,50 that extends between the machine frame 12 and each draft arm 20,22. A sensing mechanism 60 is incorporated in the hitch assembly to sense the position of the cylinders and input that position into a control mechanism that automatically adjusts the position of the implement through independent operation of the lift cylinders during operation of the machine.

Description

HITCH ASSEMBLY 2340724 This invention pertains to a hitch assembly and

more particularly to a three point hitch assembly that provides a pair of draft arms that are independently controlled with respect to one another to adjust the position of an implement with respect to a machine.

In the construction and agriculture industries it is a common practice to attach an implement to the rear of a machine to perform any one of a number of operations. In the agriculture industry in particular, it is common to attach such implements as plows or planters etc., to the rear of the machine and pull them through a field of crops. Many times the terrain is uneven and the position of the implement must be adjusted with respect to the machine in order to achieve proper operation.

In many instances the adjustment between the implement and the machine occurs in the hitch assembly that attaches the implement to the machine. Typically, a hitch, such as a three point hitch, is used that incorporates a pair of draft arms that are positioned between the machine and a hitch frame that is attached to the implement. A third link also extends between the machine and the hitch frame and is positioned above and is centred between the draft arms. The third link is adjustable in length and serves to alter the angle between the implement and the machine.

A mechanical linkage arrangement is positioned between the machine frame and the draft arms to raise and lower the draft arms. The mechanical linkage typically includes a rock shaft that is mounted on the machine frame and extends transversely between the draft arms. A pair of lift arms extend between each end of the rock shaft and the respective draft arms. The length of the lift arms is manually adjustable to allow the implement to be levelled with respect to the terrain. A lift cylinder, in the form of a hydraulic cylinder, is positioned between the machine frame and each lift arms to allow the draft arms and the implement to be raised and lowered with respect to the machine.

While this type of three point hitch configuration has been known to work quite well, it does have some drawbacks. For one thing, all of the adjustments between the implement and the machine are done by mechanical links that must be manually adjusted. The accuracy of the adjustments is limited since they are made by trail and error. Secondly, a number of components are required to permit proper adjustment and then maintain the positioning. When adjusting the level of the implement for instance, the adjustments are made and the components are fixed in place. This position is maintained by transmitting unbalanced vertical loads from side to side through the rock shaft. As these loads are transmitted from side to side, the rock shaft is subjected to relatively high torsional loads.

In order to accommodate such loading, the rock shaft and the associated components must be relatively large in size and weight. This requires a fairly complex linkage arrangement that adds significantly to the overall weight of the machine. Also the additional weight and complexity of components increases the cost of the machine not only in terms of structure, but also in manufacturing and maintenance.

The present invention is directed to overcoming one or more of the problems set forth above.

In one aspect of the present invention, a hitch assembly is provided that extends between a machine frame and an implement to attach the implement to the machine frame. A first draft arm is provided that has a first end portion pivotally mounted to the machine frame and a second end portion pivotally mounted to the implement. Likewise, a second draft arm is provided that has a first end portion pivotally mounted to the machine frame and a second end portion mounted to the implement. A link member, having a first end portion pivotally mounted to the machine frame and a second end portion mounted to the implement, is positioned such that it is elevationally above and substantially centred between the draft arms. A first fluid actuator is provided that has a first end portion pivotally mounted to the machine frame and a second end portion pivotally mounted to the first draft arm. The first fluid actuator is actuatable to move the first draft arm about its pivotal mounting to the machine frame. A second fluid actuator is provided that has a first end portion pivotally mounted to the machine frame and a second end portion pivotally mounted to the second draft arm. The second fluid actuator is actuatable to move the second draft arm about its pivotal mounting to the machine frame in a manner that is independent of the actuation of the first fluid actuator and subsequent movement of the first draft arm.

In another aspect of the present invention, a hitch assembly is adapted to mount an implement to the frame of a machine. The hitch assembly includes a hitch frame that has an attachment portion defined thereon that is adapted to engage the implement. A first draft arm is positioned to extend between and is pivotally connected with both the machine frame and a lower portion of the hitch frame on opposite ends thereof. In a similar fashion, a second draft arm is positioned to extend between and is pivotally mounted to the machine frame and a lower portion of the hitch frame on opposite ends thereof. Being so positioned, the first and second draft arms are positioned in spaced relation to one another. A link member is positioned to extend between and is pivotally mounted to each of the machine frame and an upper portion of the hitch frame. The link member is adjustable in length to vary the angle of the hitch frame with respect to the machine frame. A first fluid actuator is positioned to extend between, and is pivotally mounted to, the machine frame and the first draft arm. The first fluid actuator may be actuated to move the hitch frame along a generally vertical plane about the pivotal mounting between the first draft arm and the machine frame. A second fluid actuator is positioned to extend between and is pivotally mounted to the machine frame and the second draft arm. The second fluid actuator may be actuated to move the hitch frame along a generally vertical plane about the pivotal mounting between the second draft arm and the machine frame. A sensing mechanism is operatively connected to the hitch assembly to determine the position of the hitch frame with respect to the machine frame.

A control mechanism is operatively connected between the sensing mechanism and the first and second fluid actuators. The control mechanism causes the actuation of the first and second fluid actuators independently of one another in response to the sensing mechanism.

In yet another aspect of the present invention, a method of controlling the position of an implement with respect to a machine frame is provided. The method includes the steps of mounting the implement to the machine frame with a hitch assembly that has a pair of laterally spaced draft arms that are pivotally mounted between the machine frame and a hitch frame that is secured to the implement. A link member is pivotally mounted between the machine frame and the hitch frame at a location that is elevationally above and substantially centred between the draft arms. A second step includes the adjusting of the position of the implement along a substantially vertical plane through the independent actuation of a pair of hydraulic cylinders which are pivotally mounted between the machine frame and the respective draft arms. A third step includes the controlling of the actuation of the hydraulic cylinders through a manually adjusted controller to establish a predetermined position of the implement.

With the hitch assembly set forth above, it can be seen that control of the implement can be accomplished through the manipulation of two mechanically independent linkages which include the first and second draft arms and their associated fluid actuators. With this arrangement, adjustments may be made to the implement instantly as the machine moves through the field. Also, since a plurality of sensors are positioned in the hitch assembly, the position of the implement with respect to the machine frame may be constantly monitored. As a result, the fluid cylinders may be independently actuated during implement operation to automatically maintain a preselected position of the implement. Still further, the complex mechanical linkage arrangement required to provide lateral adjustment of the implement with respect to the machine has been eliminated. This not only reduces the number of components in the hitch assembly, it also greatly reduces the weight of the machine. This ultimately improves the balance and therefore the operation of the machine.

Two examples of hitch assemblies according to the present invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic, side view of a portion of a machine that has a hitch assembly that embodies the principles of the present invention; Fig. 2 is a diagrammatic top view of the hitch assembly shown in Fig. 1, as viewed along lines 2-2; and Fig. 3 is a diagrammatic side view of an alternate embodiment of a hitch assembly that embodies the principles of the present invention.

Referring now to the drawings, a hitch assembly is shown and is generally indicated at 10. The hitch assembly 10 is positioned to extend from the rear portion of a machine frame 12, which in the illustrated application, is an agriculture machine. The hitch assembly includes a hitch frame member 14 that defines a pair of hooks, or other attachment means 16, that engage an implement (not shown)for securely mounting it to the machine. Since the illustrated application is that of an agricultural machine, the implement may be any one of a number typically used in an agriculture environment such as a plow, disc, or planter etc. Also, it is foreseeable that the hitch frame is an integral part of the implementwith the hitch assembly being connected directly with the implement.

The hitch frame 14 is connected to the machine frame 12 along a lower portion 18 thereof by a pair of draft arms 20 and 22. The first draft arm 20 has a first end portion 24 that is pivotally mounted at 21 to the machine frame 12. A second end portion 26 of the first draft arm 20 is also pivotally mounted at 23 to a first side 28 of the hitch frame 14.

Likewise, the second draft arm 22 has a first end portion 30 pivotally mounted to the machine frame 12 and a second end portion 32 that is pivotally mounted to a second side 34 of the hitch frame that is positioned on the opposite side of the hitch frame from side 28.

A link member 36 is also positioned between the machine frame 12 and the hitch frame 14. A first end portion 38 of the link member is pivotally mounted to the machine frame while a second end portion 40 is pivotally mounted to the hitch frame. The link member 36 is adjustable in length so that the hitch frame may be rotated about its mounting with the respective draft arms 20 and 22 to adjust the angle of the hitch frame, and therefore the implement, with respect to the machine frame. The length may be adjusted in any suitable manner such as a turnbuckle type connection between the first and second end portions 38 and 40, or a manually actuated, grease filled cylinder. While not shown, it is to be understood that the link member could also be a hydraulic cylinder and still be within the scope of the present invention.

The first draft arm 20 may be rotated about its mounting 21 with the machine frame 12 by a first fluid actuator, such as a hydraulic cylinder 44, which is shown in the illustrated embodiment. The hydraulic cylinder has a first, or cylinder, end portion 46 that is pivotally mounted to the machine frame 12 and a second, or rod, end portion 48 that is pivotally mounted to the first draft arm 20. In a similar manner, a second fluid actuator, also shown to be a hydraulic cylinder 50 is mounted between the machine frame and the second draft arm 22. The second hydraulic cylinder 50 has a first, or cylinder end portion 52, that is pivotally mounted to the machine frame, while a second, or rod end portion 54, is pivotally mounted to the second draft arm 22. Each of the hydraulic cylinders 46 and 50 are independently actuated so that each side portion 28 and 34 respectively, of the hitch frame 14 may be independently adjusted with respect to the machine frame. When such an adjustment is made, the lateral angularity of the hitch frame 14, and therefore the implement, may be adjusted with respect to the machine frame.

It should be noted that the pivotal mountings 21 and 23 between the draft arms and the machine and hitch frames are of the ball joint or spherical bearing type so that a significant degree of misalignment between the various components may be accommodated. In the illustrated embodiment, misalignment may occur in both the transverse and longitudinal planes with respect to the machine.

A sensing mechanism 60 is provided in the respective mountings 21 and 23 of the draft arms 20 and 22 so that the position of the draft arms, and thereby the implement, is monitored at all times. In the drawings, a rotary sensor 62 is shown to be positioned at one or both of the pivotal mountings 21 and 23. While a rotary-type sensor of any well known type is sufficient for the intended purpose, it is also contemplated that any other of several position sensors could be utilized without departing from the intent of the subject invention. For example, a position sensor could be mounted on or within one or both of the hydraulic cylinders 44 and 50 to determine the amount of extension of the respective rod end portions and thereby be utilized to determine the position of the hitch frame andlor implement.

Turning now to Fig. 3, a control mechanism 64 for the hitch assembly 10 is shown schematically. The control mechanism 64 utilizes and engine driven pump 66 to communicate hydraulic fluid from a tank 68 to one or both of a pair of control valves 70 and 72 via conduits 74, 76 and 78. Each control valve is a three position valve of well known configuration and that communicates fluid between the respective hydraulic cylinders 44 and 50. Specifically, fluid is communicated between the first control valve 70 and the first cylinder 44 via a pair of conduits 80 and 82. In a similar manner, fluid is communicated between the second control valve 72 and the second hydraulic cylinder 50 via conduits 84 and 86.

Each of the control valves 70 and 72 is controlled by an electrically actuated pair of solenoids and 92,94 that are positioned on opposite ends of the respective valves. The first valve 70 has a pair of solenoids 88 and 90 that are connected to a microprocessor 96, having a well known configuration, by a pair of wires 98 and 100 respectively. The second control valve 72 has a pair of solenoids 92 and 94 that are also connected to the microprocessor 96 by a pair of wires 102 and 104. Upon actuation of any one of the respective solenoids, the valves may be shifted from a centre position wherein communication of pressurized fluid with the respective hydraulic cylinders is blocked to a position wherein pressurized fluid is communicated to either of the head or rod end of the cylinder while the other end is communicated to the tank.

The sensors which are illustrated in Fig. 3 by S1 and s2 are also connected to the microprocessor 96 by wires 106 and 108 respectively. The control mechanism 64 is operational in a mode wherein the input from the sensors is read by the microprocessor which in turn, will cause an appropriate actuation of one or both of the hydraulic cylinders 44 and 50. A control member 110 is also shown to be connected to the microprocessor via wire 112. The control member 110 may be positioned in the operator station of the machine and may be utilized to adjust the position of the implement during machine operation. In the illustrated embodiment, the control member 110 is shown to be a potentiometer-type control member wherein the rotation of the control member in a clockwise direction will cause actuation of the cylinders 44 and 50 to angle the hitch frame 14, and thus the implement, in a clockwise direction as viewed from the rear of the machine. The more the control lever is rotated, the more the degree of tilt of the implement. Likewise, should the control lever be rotated in the opposite direction, the implement would be rotated in a corresponding fashion. A second control lever 114 may also be positioned in the operator station to cause the simultaneous actuation of the cylinders to raise and lower the implement. It is contemplated that the microprocessor may be selectively operated in a mode wherein the control lever 114 will establish a preselected angle for the implement and the sensors s1 and C will be utilized to cause the actuation of the respective cylinders 44 and 50 to reposition the implement back to that preselected position in the event that the draft arms 20 and 22 become repositioned during the operation of the machine. Alternatively, a purely manual mode of operation, absent the automatic repositioning of the sensors, is also envisioned.

During the operation of a machine, such as an agricultural machine, that may utilize the hitch assembly 10, there are some options that the operator may consider. In many instances, the terrain over which the machine and implement will operate be uneven. These instances occur when operating across the face of a hillside, or when the machine will have its tracks or wheels on one side of the machine in a furrow or otherwise at a different level than the wheels on the other side of the machine. In these situations, the operator will want to angle the implement in a transverse direction with respect to the machine to achieve an appropriate angle for the implement to operate. To do so, the operator may rotate the control member 110 in either direction, depending on the direction of desired adjustment. If it is desirable to angle the implement in a clockwise direction when looking at the rear of the machine, the operator can rotate the control member in a clockwise direction to affect such a result. The more the control member is rotated, the more the implement will be angled.

When the control member 110 is rotated, an input is sent via wire 112 to the microprocessor 96. The microprocessor in turn, will actuate the solenoid 88 to move the first control valve 70 upward as viewed in Fig. 3. In this position, pressurized fluid is directed from the pump 66 to the head end 46 of the first cylinder 44. At the same time the rod end 48 will be communicated with the tank 68 and the cylinder will extend to a preselected amount established by the rotation of the control member. When the first cylinder is extended, the first draft arm 20 will be raised with respect to the second draft arm 22, causing the hitch frame 14 and thus the attached implement to be angled with respect to the machine and/or the ground. Angling the implement in the opposite direction would require the similar actuation of the second control valve 72 and the second cylinder by rotating the control member 110 in a counter-clockwise direction. It is also possible to create an angled condition by extending one cylinder to raise one draft arm and retract the other cylinder to lower the other draft arm.

In the event that the operator need to raise or lower the implement, the control lever 114 may be moved to cause the simultaneous extension or retraction of the cylinders 44 and 50. For example to raise the cylinders, actuation of solenoids 88 and 92 of the respective control valves 70 and 72 is initiated to reposition the control valves to communicate pressurized fluid to the head ends 46 and 52 of the respective cylinders 44 and 50. Actuation of the other of the solenoids 90 and 94 will direct pressurized fluid to the rod ends 48 and 54 of the respective cylinders to cause them to retract, thus lowering the cylinders and therefore the implement.

Should the operator desire to maintain the angle of the implement at a preselected throughout the operation of the machine, the microprocessor 96 may be utilized to automatically control the lift cylinders 44 and 50 through input from the sensing mechanism 60. In this mode, the sensors sl and s2, in the form of rotary sensors 62 shown in this embodiment, are positioned about the pivotal mountings 21 and 23 between the respective draft arms 20 and 22 and the machine frame 12. The sensors provide input to the microprocessor so that the position of the draft arms can be determined at all times. There are times during the operation of the machine when the machine is operating on an angle and it is desirable to maintain the implement at a different angle.

Such a condition would exist during a plowing operation when one set of wheels or tracks is positioned in a furrow while the other is positioned on unplowed ground. It is desirable during this operation to maintain the implement, which in this instance would be the plow, at an attitude that is parallel to the ground being plowed. The sensors would be able to input any changes in the position of the draft arms into the microprocessor 96 which would in turn automatically actuate the corresponding solenoids 88, 90, 92 and 94 in a manner that will maintain the desired position of the implement. Another situation in which automatic operation would be desirable would exist when the machine, during a plowing operation, would encounter a depression in the terrain or a ditch. The machine, being much narrower than the plow, would precede the plow into the depression or ditch.

Typically, this would cause the draft arms to drive the plow into the soil as the machine enters the ditch. The rotary sensors in the draft arm would sense this condition and cause the lift arms to elevate to maintain the attitude of the plow with respect to the terrain even if the machine were elevationally lower.

With a hitch arrangement as set forth above, adjustment of the implement with respect to the ground is greatly simplified since it may be done as the machine is moving.

With the simplification of operation also comes a simplification in structure, since a plurality of mechanically adjustable links formerly required to manually adjust the attitude of the implement have been eliminated. Finally, the automatic repositioning of the implement with respect to the terrain through the use of the sensing mechanism greatly simplifies the operation of the implement and the machine.

Claims

1 A hitch assembly adapted for mounting an implement to a machine, comprising:

a first draft arm having a first end portion pivotally mountable to the machine and a second end portion pivotally mountable to the implement; a second draft arm having a first end portion pivotally mountable to the machine frame and a second end portion pivotally mountable to the implement, said first and second draft arms being mounted in generally spaced, parallel relation to one another; a link member having a first end portion pivotally mountable to the machine frame and a second end portion pivotally mountable to the implement at a location that is substantially centred between the first and second draft arms and spaced elevationally thereabove; a first fluid actuator having a first end portion pivotally mountable to the machine frame and a second end portion pivotally mounted to the first draft arm, said first fluid actuator being actuatable to move the first draft arm about its pivotal mounting to the machine frame; a second fluid actuator having a first end portion pivotally mounted to the machine frame and a second end portion pivotally mounted to the second draft arm, said second fluid actuator being actuatable to move the second draft arm about its pivotal mounting to the machine frame, said second fluid actuator being adapted for actuation independently of said first fluid actuator.

2. The hitch assembly as set forth in claim 1 wherein the first and second draft arms are mounted to laterally opposite sides of a hitch frame that is defined by the hitch assembly and extends in a transverse orientation with respect to the machine.

3. The hitch assembly as set forth in claim 1 wherein the link member is adjustable in a manner wherein it may be lengthened or shortened in order to change the angle of the implement with respect to the machine frame.

4. The hitch assembly as set forth in claim 1 wherein the pivotal mountings between the first and second end portions of the first and second draft arms and the respective machine and the implement are of the spherical bearing type to permit misalignment therebetween in at least two planes.

-g-

5. The hitch assembly as set forth in claim 1 wherein first and second valve members are operatively connected to the first and second fluid actuators to provide independent actuation of the respective fluid actuators.

6. The hitch assembly as set forth in claim 5 wherein a sensing mechanism is operatively associated with the pivotal mounting between the first and second draft arms and the machine frame to determine the relative position of the respective draft arms with respect to the machine frame.

7. The hitch assembly as set forth in claim 6 wherein a control mechanism is adapted for communication with the sensing mechanism and the first and second valve members to control the movement of one or both of the fluid actuators in response to movement of the first and second draft arms caused by movement of the implement.

8. The hitch assembly as set forth in claim 7 wherein the control mechanism includes a controller for establishing a predetermined position of the first and second fluid actuators, said sensing mechanism being adapted to provide input to the control mechanism when either one or both of the draft arms are repositioned by the implement, said control mechanism being adapted to control the actuation of the fluid actuators to reposition the draft arms to their predetermined position.

9. The hitch assembly as set forth in claim 6 wherein the fluid actuators include a hydraulic cylinder having a cylinder portion and a rod portion that extends from the cylinder portion and is mounted for reciprocating movement with respect to the cylinder portion.

10. The hitch assembly as set forth in claim 9 wherein the sensing mechanism is associated with the hydraulic cylinders to determine the position of the rod portion with respect to the cylinder portion and provide actuation of one or both of the hydraulic cylinders in response to said positioning.

11. A hitch assembly adapted to mount an implement to the frame of a machine, comprising:

a hitch frame having an attachment portion defined thereon, said attachment portion adapted to engage the implement; a first draft arm extending between and pivotally mounted to each of the machine frame and a lower portion of the hitch frame on opposite ends thereof; a second draft arm extending between and pivotally mounted to each of the machine frame and a lower portion of the hitch frame on opposite ends thereof, said second draft arm being spaced laterally from the first draft arm; _.

a link member extending between and pivotally mounted to each of the machine frame and an upper portion of the hitch frame, said link member being adjustable in length to vary the angle of the hitch frame with respect to the ine frame; a first fluid actuator extending between and pi ly mounted to the machine frame and the first draft arm to move the hitch frame ong a generally vertical plane about the pivotal mounting between the first draft arm and the machine frame; a second fluid actuator extending between and pivotally mounted to the machine frame and the second draft arm to move the hitch frame along a generally vertical plane about the pivotal mounting between the second draft arm and the machine frame; a sensing mechanism operatively connected to the hitch assembly to determine the position of the hitch frame with respect to the machine frame; and a control mechanism operatively connected between the sensing mechanism and the first and second fluid actuators for causing the actuation of the first and second fluid actuators independently of one another in response to the sensing mechanism.

12. The hitch assembly as set forth in claim 11 wherein the sensing mechanism includes a rotary sensor positioned within the pivotal mounting between the machine frame and each of the first and second draft arms.

13. The hitch assembly as set forth in claim 11 wherein the fluid actuators include hydraulic cylinders having a cylinder portion mounted to one of the machine frame and the respective draft arms and a rod portion pivotally mounted to the other of the machine frame and the respective draft arms, said rod portion being moveable for reciprocation within the cylinder portion.

13. The hitch assembly as set forth in claim 12 wherein the sensing mechanism includes a sensor operatively connected to each of the fluid actuators to determine the position of the rod portion with respect to the cylinder portion.

14. The hitch assembly as set forth in claim 11 wherein a control mechanism having a controller and a pair of electro-hydraulic valves is operatively connected with the respective fluid actuators and sensing mechanism to establish a predetermined position of the hitch frame with respect to the machine frame and maintain said preselected position through independent actuation of the respective fluid actuators.

15.A method of controlling the position of an implement with respect to a machine frame, comprising the steps of:

mounting the implement to the machine frame with a hitch assembly having a pair of laterally spaced draft arms pivotally mounted between the machine frame and a hitch frame secured to the implement and a link member pivotally mounted between the machine frame and the hitch frame at a location that is elevationally above and substantially centred between said draft arms; adjusting the position of the implement along a substantially vertical plane through the independent actuation of a pair of hydraulic cylinders, each cylinder being pivotally mounted between the machine frame and the respective draft arms; and controlling the actuation of the hydraulic cylinders through a manually adjusted controller to establish a predetermined position of the implement.

16. The method as set forth in claim 15 further comprising the steps of:

sensing the movement of the implement from the preselected position; and adjusting the position of the draft arms through independent actuation of the hydraulic cylinders to reposition the implement to the preselected position.

17. A hitch assembly according to claim 1 or claim 11, substantially as described with reference to the accompanying drawings.