HYDRAULIC SYSTEM FOR LEG ASSEMBLY OF WORK MACHINE

Description

TECHNICAL FIELD

The present disclosure relates to a work machine, and more particularly, to a hydraulic system for a leg assembly of the work machine and a method for controlling a movement of the leg assembly of the work machine.

BACKGROUND

A work machine, such as a cold planer or a reclaimer, is often used to perform milling, reclaiming, or stabilization operations at various surfaces, such as streets, highways, aircraft runways, and the like. The work machine includes a number of ground engaging members that may raise or lower as required. The work machine also includes a rotor that contacts with a work surface to perform work operations. The work machine further includes a number of leg assemblies. The leg assemblies are movable between an extended state and a retracted state to raise or lower the ground engaging members and/or the rotor.

Typically, in the retracted state of the leg assemblies, the leg assemblies lower the work machine and the rotor to provide a desired depth of cut in a work surface. Each leg assembly from the leg assemblies includes an actuator that receives a pressurized hydraulic fluid to move the corresponding leg assembly from the extended state to the retracted state. However, if the rotor does not cut at the desired depth into the work surface, the leg assemblies may retract in the air. In such instances, the leg assemblies and/or the ground engaging members may lift from the work surface, which may impact a stability of the work machine. Further, in some instances, the rotor may continue to cut the work surface, before the lifted leg assemblies and/or the ground engaging members make contact with the work surface, which may result in an undesired divot on the work surface.

U.S. Patent Number 3,888,542 describes an apparatus for machining road surfaces of the kind comprising a body having road wheels and carrying a cutting drum mounted for rotation about an axis extending transversely of the direction of travel and movable into contact with a road surface to cut away a layer of the surface in which there is a first hydrostatic pump, connected to a hydrostatic motor for driving the drum in which there is a second hydrostatic pump connected to a hydrostatic motor for driving at least one of the road wheels and in which there is means to drive both of the pumps at constant speed, and both of the pumps have infinitely variable displacements, means being provided for varying the displacements of the pumps individually whereby any combination of drum and road wheel speeds may be provided.

SUMMARY OF THE DISCLOSURE

In an aspect of the present disclosure, a hydraulic system for a leg assembly of a work machine is provided. The leg assembly includes an actuator that is adapted to retract to move the leg assembly from an extended state to a retracted state. The actuator defines a rod end and a head end. The hydraulic system includes a pump. The hydraulic system also includes a tank adapted to store fluid. The hydraulic system further includes a main control valve adapted to be disposed in selective fluid communication with each of the pump and the tank. The hydraulic system includes a first valve disposed upstream of the head end of the actuator. The first valve is adapted to be disposed in selective fluid communication with the pump via the main control valve. The hydraulic system also includes a second valve disposed upstream of the rod end of the actuator. The second valve is adapted to be disposed in selective fluid communication with at least one of the pump, via the main control valve, and the tank. The second valve is adapted to selectively control a fluid flow from at least one of the tank and the pump towards the rod end of the actuator to retract the actuator.

In another aspect of the present disclosure, a work machine is provided. The work machine includes a frame. The work machine also includes at least two ground engaging members adapted to move between a lowered position and a raised position. The work machine further includes at least two leg assemblies. Each ground engaging member from the at least two ground engaging members is movable by a corresponding leg assembly from the at least two leg assemblies. Each of the at least two leg assemblies includes a first tube. Each of the at least two leg assemblies also includes a second tube disposed within the first tube and movable relative to the first tube. Each of the at least two leg assemblies further includes an actuator that is adapted to retract to move the leg assembly from an extended state to a retracted state. The actuator defines a head end and a rod end. Each of the at least two leg assemblies includes a hydraulic system for controlling the at least two leg assemblies. The hydraulic system includes a pump. The hydraulic system also includes a tank adapted to store fluid. The hydraulic system further includes a main control valve adapted to be disposed in selective fluid communication with each of the pump and the tank. The hydraulic system includes a first valve disposed upstream of the head end of the actuator. The first valve is adapted to be disposed in selective fluid communication with the pump via the main control valve. The hydraulic system also includes a second valve disposed upstream of the rod end of the actuator. The second valve is adapted to be disposed in selective fluid communication with at least one of the pump, via the main control valve, and the tank. The second valve is adapted to selectively control a fluid flow from at least one of the tank and the pump towards the rod end of the actuator to retract the actuator.

In yet another aspect of the present disclosure, a method for controlling a movement of a leg assembly of a work machine is provided. Each leg assembly includes an actuator. The actuator defines a head end and a rod end. The method includes providing a main control valve of a hydraulic system of the work machine. The hydraulic system further includes a pump and a tank adapted to store fluid. The method also includes providing a first valve of the hydraulic system. The first valve is disposed upstream of the head end of the actuator. The first valve is adapted to be disposed in selective fluid communication with the pump via the main control valve. The method further includes providing a second valve of the hydraulic system. The second valve is disposed upstream of the rod end of the actuator. The second valve is adapted to be disposed in selective fluid communication with at least one of the pump, via the main control valve, and the tank. The method includes controlling, by a controller of the hydraulic system, the main control valve to supply a pilot fluid flow towards the first valve. The controller is communicably coupled with the main control valve and the second valve. The method also includes actuating, based on the supply of the pilot fluid flow, the first valve. The method further includes causing fluid to flow from the head end of the actuator towards the tank, based on the actuation of the first valve. The method includes controlling, by the controller, at least one of the main control valve and the second valve to allow a fluid flow from at least one of the tank and the pump towards the rod end of the actuator. The method also includes retracting the actuator based on the flow of the fluid from the head end of the actuator towards the tank and the fluid flow from at least one of the tank and the pump towards the rod end of the actuator.

Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of a work machine, according to an example of the present disclosure;

FIG. 2 is a sectional view of a leg assembly disposed at a front end of the work machine of FIG. 1, according to an example of the present disclosure;

FIGS. 3 and 4 are schematic views of a hydraulic system for the leg assembly of FIG. 2, according to an example of the present disclosure; and

FIG. 5 is a flowchart for a method for controlling a movement of the leg assembly of the work machine of FIG. 1, according to an example of the present disclosure.

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Referring to FIG. 1, a schematic side view of an exemplary work machine 100 is illustrated. The work machine 100 is embodied as a cold planer herein. The work machine 100 may perform one or more work operations associated with an industry, such as, mining, construction, farming, transportation, or any other industry known in the art. The work machine 100 is operating at a worksite 102. The worksite 102 may include, for example, a mine site, a quarry, a construction site, or any other type of worksite. The work machine 100 may be used to remove, mix, or reclaim material from a work surface 106. The work surface 106 may include, for example, a roadway. Further, the work machine 100 may be a manned machine or an unmanned machine. In some examples, the work machine 100 may be a machine having various levels of autonomy, such as a fully autonomous machine, a semi-autonomous machine, a remotely operated machine, or a remotely supervised machine. The work machine 100 may include a reclaimer, a stabilizer, or any other machine that includes leg assemblies.

The work machine 100 defines a front end 108 and a rear end 110 opposite the front end 108. The work machine 100 includes a frame 112 that supports various machine components thereon. The work machine 100 further includes a power source (not shown) that generates power. The power source may be an engine, such as, an internal combustion engine, a battery system, a fuel cell, and the like. The power source is mounted on the frame 112. The power source is disposed within an enclosure 114.

The work machine 100 also includes a number of ground engaging members 116, 117. The number of ground engaging members 116, 117 move between a lowered position and a raised position. The work machine 100 includes the two or more ground engaging members 116 that are disposed proximal to the front end 108 of the work machine 100. The work machine 100 also includes the two or more ground engaging members 117 that are disposed proximal to the rear end 110 of the work machine 100. In the illustrated example of FIG. 1, the work machine 100 includes two ground engaging members 116 (only one of which is shown in FIG. 1) disposed at the front end 108 of the work machine 100 and two ground engaging members 117 (only one of which is shown in FIG. 1) disposed at the rear end 110 of the work machine 100. Each ground engaging member 116, 117 is embodied as a track herein. Alternatively, the work machine 100 may include wheels instead of tracks. In the illustrated example of FIG. 1, each ground engaging member 116, 117 is illustrated in the lowered position.

The work machine 100 also includes a work tool 118 for milling the work surface 106. The work tool 118 includes a rotor herein. The rotor includes a rotatable drum and a number of tools disposed on the rotatable drum. The work machine 100 further includes a milling chamber 124. The milling chamber 124 may be supported by the frame 112 of the work machine 100 and may be defined under the frame 112 of the work machine 100. The milling chamber 124 encloses the work tool 118 such that disintegrated particles produced during the milling operation may be restrained and confined within the milling chamber 124.

The work machine 100 includes a loading conveyor 120. After being cut by the work tool 118, the material removed from the work surface 106 may enter the loading conveyor 120 which may transfer the removed material into a dump truck (not shown) or other suitable machine for transporting the material. In some cases, the removed material can also be cast off to a side for pick-up or re-use at the worksite 102.

The work machine 100 further includes an operator station 122 supported by the frame 112. An operator of the work machine 100 may sit or stand in the operator station 122 to overlook machine operations. The operator station 122 may also include various control devices to control one or more operations of the work machine 100.

The work machine 100 further includes two or more leg assemblies 128, 130. Specifically, the work machine 100 includes four leg assemblies 128, 130 (only two of which are shown in FIG. 1). The two leg assemblies 128 are disposed proximal to the front end 108 of the work machine 100. Further, the two leg assemblies 130 are disposed proximal to the rear end 110 of the work machine 100. Each ground engaging member 116, 117 from the two or more ground engaging members 116, 117 is movable by a corresponding leg assembly 128, 130 from the two or more leg assemblies 128, 130. Particularly, the ground engaging members 116 are movable by the leg assemblies 128 and the ground engaging members 117 are movable by the leg assemblies 130.

Referring to FIG. 2, a sectional view of the leg assembly 128 is illustrated. It should be noted that the details provided herein may be equally applicable to the leg assemblies 130. Each of the two or more leg assemblies 128 includes a first tube 202. Each of the two or more leg assemblies 128 also includes a second tube 204 disposed within the first tube 202 and movable relative to the first tube 202. Each of the two or more leg assemblies 128 further includes an actuator 206. The actuator 206 retracts to move the leg assembly 128 from an extended state to a retracted state. Further, the actuator 206 extends to move the leg assembly 128 from the retracted state to the extended state. In the illustrated example of FIG. 2, the actuator 206 is illustrated in the extended state.

Referring to FIG. 3, the actuator 206 defines a head end 208 and a rod end 210. Specifically, the actuator 206 includes a cylinder 212 defining the head end 208 and the rod end 210. The actuator 206 also includes a rod 214 that is slidable relative to the cylinder 212.

FIG. 3 illustrates a schematic view of a hydraulic system 300 for the leg assembly 128 of the work machine 100 of FIG. 1, according to an example of the present disclosure. Specifically, the work machine 100 includes the hydraulic system 300 for controlling the two or more leg assemblies 128. The hydraulic system 300 described herein is associated to the leg assembly 128 that is disposed at the front end 108 (see FIG. 1) of the work machine 100. However, the hydraulic system 300 described herein may be associated with the leg assemblies 130.

The hydraulic system 300 includes a pump 302. The hydraulic system 300 also includes a tank 304 to store fluid. In some examples, the fluid may be oil, water, or any other hydraulic fluid, without limiting the scope of the present disclosure. The hydraulic system 300 further includes a main control valve 306 disposed in selective fluid communication with each of the pump 302 and the tank 304. The main control valve 306 is disposable in selective fluid communication with the actuator 206 via the head end 208 and the rod end 210. In some examples, the main control valve 306 may include a solenoid valve. The hydraulic system 300 further includes a check valve 314 disposed downstream of the main control valve 306.

The hydraulic system 300 also includes a first valve 308 disposed upstream of the head end 208 of the actuator 206. The first valve 308 is disposed in selective fluid communication with the pump 302 via the main control valve 306.

The hydraulic system 300 further includes a second valve 310 disposed upstream of the rod end 210 of the actuator 206. In some examples, each of the first valve 308 and the second valve 310 is a counterbalance valve. Further, the second valve 310 is a solenoid operated valve. The second valve 310 is disposed in selective fluid communication with the pump 302, via the main control valve 306, and/or the tank 304. The second valve 310 selectively controls a fluid flow from the tank 304 and/or the pump 302 towards the rod end 210 of the actuator 206 to retract the actuator 206.

The hydraulic system 300 further includes a controller 312 communicably coupled with the main control valve 306 and the second valve 310. The controller 312 controls an operation of the main control valve 306 and the second valve 310. The controller 312 includes one or more memories (not shown) and one or more processors (not shown). The memories may include any means of storing information, including a hard disk, an optical disk, a floppy disk, ROM (read only memory), RAM (random access memory), PROM (programmable ROM), EEPROM (electrically erasable PROM), or other computer-readable memory media.

It should be noted that the processors may embody a single microprocessor or multiple microprocessors for receiving various input signals and generating output signals. Numerous commercially available microprocessors may perform the functions of the processors. The processors may further include a general processor, a central processing unit, an application specific integrated circuit (ASIC), a digital signal processor, a field programmable gate array (FPGA), a digital circuit, an analog circuit, a microcontroller, any other type of processor, or any combination thereof. The processors may include one or more components that may be operable to execute computer executable instructions or computer code that may be stored and retrieved from the memories.

In the illustrated example of FIG. 3, to retract the actuator 206, the first valve 308 receives a pilot fluid flow F1 from the pump 302, via the main control valve 306, to actuate the first valve 308. An actuation of the first valve 308 causes fluid to flow from the head end 208 of the actuator 206 towards the tank 304. The flow of fluid from the head end 208 to the tank 304 causes the actuator 206 to retract due to gravity and/or machine weight to lower the work tool 118 of the work machine 100 into the work surface 106. It should be noted that the fluid flowing out of the cylinder 212 is directed to the tank 304 via the main control valve 306.

Further, the controller 312 controls the second valve 310 to allow the fluid flow from the tank 304 towards the rod end 210 of the actuator 206 to retract the actuator 206. The fluid flow towards the rod end 210 of the actuator 206 compensates for a volume change within the cylinder 212 of the actuator 206 during the retraction of the actuator 206. Thus, the fluid is received within the cylinder 212 of the actuator 206 from the tank 304, via the second valve 310, and the fluid flows out of the cylinder 212 via the head end 208 of the actuator 206. It should be noted that a state in which the main control valve 306, the first valve 308, and the second valve 310 are disposed and explained in relation to FIG. 3 causes the work machine 100 to lower, causes the work tool 118 to be inserted into the work surface 106, and/or prevents the ground engaging member 116 from lifting if the work tool 118 is not cutting into the work surface 106 faster than a lowering speed or if doors of the milling chamber 124 or any other machine component holds up the work machine 100.

Referring now to FIG. 4, to retract the actuator 206, the first valve 308 receives the pilot fluid flow F1 from the pump 302, via the main control valve 306, to actuate the first valve 308. The actuation of the first valve 308 causes fluid to flow from the head end 208 of the actuator 206 towards the tank 304 to move a corresponding ground engaging member 116 from the number of ground engaging members 116 from the lowered position to the raised position and to lower the work tool 118 of the work machine 100 into the work surface 106. It should be noted that the fluid flowing out of the cylinder 212 is directed to the tank 304 via the main control valve 306.

Further, the controller 312 controls each of the main control valve 306 and the second valve 310 to allow to the fluid flow from the pump 302 towards the rod end 210 of the actuator 206, via the main control valve 306, to move the corresponding ground engaging member 116 from the number of ground engaging members 116 from the lowered position to the raised position and to lower the work tool 118 of the work machine 100 into the work surface 106. Thus, the fluid is received within the cylinder 212 of the actuator 206 from the pump 302, via the main control valve 306 and the second valve 310, and the fluid flows out of the cylinder 212 via the head end 208 of the actuator 206. It should be noted that a state in which the main control valve 306, the first valve 308, and the second valve 310 are disposed and explained in relation to FIG. 4 causes the work machine 100 to lower, causes the work tool 118 (see FIG. 1) to be inserted into the work surface 106, and/or can be used to lift the corresponding ground engaging member 116 in the raised position for service if the work machine 100 is supported on stands. It should be noted that, in such an example, the check valve 314 may hold the corresponding ground engaging member 116 in the raised position.

It is to be understood that individual features shown or described for one embodiment may be combined with individual features shown or described for another embodiment. The above-described implementation does not in any way limit the scope of the present disclosure. Therefore, it is to be understood although some features are shown or described to illustrate the use of the present disclosure in the context of functional segments, such features may be omitted from the scope of the present disclosure without departing from the spirit of the present disclosure as defined in the appended claims.

INDUSTRIAL APPLICABILITY

The present disclosure is related to the hydraulic system 300 for the leg assembly 128 of the work machine 100. The hydraulic system 300 includes the first valve 308 and the second valve 310.

In one example, as explained in relation to FIG. 3, the hydraulic system 300 allows retraction of the leg assembly 128 due to gravity and/or weight of the work machine 100 to lower the work machine 100 and the work tool 118 into the work surface 106. Specifically, the hydraulic system 300 allows the retraction flow from the actuator 206 to be open to the tank 304 and also allows the pump 302 to transmit the pilot fluid flow F1 to actuate the first valve 308. Further, the controller 312 controls the second valve 310 to allow the fluid flow from the tank 304 towards the rod end 210 of the actuator 206 to retract the actuator 206. This helps the work machine 100 to lower due to gravity, while the second valve 310 is connected to the tank 304. In such an example, the hydraulic system 300 may allow the work machine 100 to be lowered to insert the work tool 118 into the work surface 106 and may prevent the ground engaging members 116 from lifting off the work surface 106, if the work tool 118 is not cutting into the work surface 106 faster than the lowering speed or if doors of the milling chamber 124 or any other machine component holds up the work machine 100. Specifically, the actuation of the first valve 308 causes fluid to flow from the head end 208 of the actuator 206 towards the tank 304 that causes the actuator 206 to retract due to gravity and/or machine weight to lower the work tool 118 of the work machine 100 into the work surface 106.

In another example, as explained in relation to FIG. 4, when it is desired to lift the ground engaging member 116 off the work surface 106, in addition to lowering the work machine 100 and inserting the work tool 118 into the work surface 106, the second valve 310 is connected to the pump 302 to provide the fluid flow towards the rod end 210 to retract the cylinder 212 which may cause lifting of the ground engaging member 116 off the work surface 106. In such an example, the hydraulic system 300 allows the movement of the ground engaging member 116 from the lowered position to the raised position. The hydraulic system 300 may allow service operation of the work machine 100 if the work machine 100 is supported on stands.

The hydraulic system 300 may optimize an operation of the work machine 100 and may reduce a downtime of the work machine 100. The hydraulic system 300 may improve a stability of the work machine 100 that may otherwise be impacted due to an inadvertent lifting of the ground engaging members 116 in air. The hydraulic system 300 may control the movement of the leg assemblies 128 and/or the ground engaging members 116, thereby preventing undesired divot on the work surface 106.

Overall, the hydraulic system 300 is simple in design as the hydraulic system 300 does not include complex components. Moreover, the hydraulic system 300 may be cost-effective, may be time efficient, and may be retrofitted to existing work machines.

FIG. 5 is a flowchart for a method 500 for controlling the movement of the leg assembly 128 of the work machine 100. With reference to FIGS. 1 to 5, at step 502, the main control valve 306 of the hydraulic system 300 of the work machine 100 is provided. The hydraulic system 300 further includes the pump 302 and the tank 304 to store fluid.

At step 504, the first valve 308 of the hydraulic system 300 is provided. The first valve 308 is disposed upstream of the head end 208 of the actuator 206. The first valve 308 is disposed in selective fluid communication with the pump 302 via the main control valve 306.

At step 506, the second valve 310 of the hydraulic system 300 is provided. The second valve 310 is disposed upstream of the rod end 210 of the actuator 206. The second valve 310 is disposed in selective fluid communication with the pump 302, via the main control valve 306, and/or the tank 304.

At step 508, the controller 312 of the hydraulic system 300 controls the main control valve 306 to supply the pilot fluid flow F1 towards the first valve 308. The controller 312 is communicably coupled with the main control valve 306 and the second valve 310.

At step 510, based on the supply of the pilot fluid F1 flow the first valve 308 is actuated.

At step 512, based on the actuation of the first valve 308 fluid is caused to flow from the head end 208 of the actuator 206 towards the tank 304.

At step 514, the controller 312 controls the main control valve 306 and/or the second valve 310 to allow the fluid flow from the tank 304 and/or the pump 302 towards the rod end 210 of the actuator 206.

At step 516, the actuator 206 is retracted based on the flow of the fluid from the head end 208 of the actuator 206 towards the tank 304 and the fluid flow from the tank 304 and/or the pump 302 towards the rod end 210 of the actuator 206. The step 516 further includes causing the actuator 206 to retract due to gravity and/or machine weight to lower the work tool 118 of the work machine 100 into the work surface 106.

The method 500 further includes a step (not shown) at which the controller 312 controls the second valve 310 to allow the fluid flow from the tank 304 towards the rod end 210 of the actuator 206. The step of controlling, by the controller 312, the second valve 310 to allow the fluid flow from the tank 304 towards the rod end 210 of the actuator 206 further includes compensation, based on the fluid flow towards the rod end 210 of the actuator 206, of the volume change within the cylinder 212 of the actuator 206 during the retraction of the actuator 206.

The method 500 further includes a step (not shown) at which the actuator 206 is retracted based on the flow of the fluid from the head end 208 of the actuator 206 towards the tank 304 and the fluid flow from the tank 304 towards the rod end 210 of the actuator 206. Further, the step at which the actuator 206 retracts based on the flow of the fluid from the head end 208 of the actuator 206 towards the tank 304 and the fluid flow from the tank 304 towards the rod end 210 of the actuator 206 further includes retraction of the actuator 206 due to gravity and/or machine weight to lower the work tool 118 of the work machine 100 into the work surface 106.

The method 500 further includes a step (not shown) at which the leg assembly 128 is moved from the extended state to the retracted state based on the retraction of the actuator 206.

The work machine 100 includes the number of ground engaging members 116 that move between the lowered position and the raised position. The method 500 further includes a step (not shown) at which the controller 312 controls each of the main control valve 306 and the second valve 310 to allow the fluid flow from the pump 302 towards the rod end 210 of the actuator 206 via the main control valve 306. The method 500 further includes a step (not shown) at which the actuator 206 is retracted based on the flow of the fluid from the head end 208 of the actuator 206 towards the tank 304 and the fluid flow from the pump 302 towards the rod end 210 of the actuator 206. The method 500 further includes a step (not shown) at which the corresponding ground engaging member 116 from the number of ground engaging members 116 is moved from the lowered position to the raised position and to lower the work tool 118 of the work machine 100 into the work surface 106 based on the retraction of the actuator 206.

It should be noted that the steps 502, 504, 506, 508, 510, 512, 514, 516 of the method 500 may be performed in a sequence that is different from that explained in relation to FIG. 5. Further, various steps 502, 504, 506, 508, 510, 512, 514, 516 can be performed together.

While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed work machine, systems and methods without departing from the spirit and scope of the disclosure. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.