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DE-102025145871-A1 - HYDRAULIC SYSTEM FOR THE LEG MOUNTING OF A WORK MACHINE

DE102025145871A1DE 102025145871 A1DE102025145871 A1DE 102025145871A1DE-102025145871-A1

Abstract

A hydraulic system (300) for a leg assembly (128, 130) of a working machine (100) comprises a pump (302), a tank (304), and a main control valve (306) that is selectively connected to the pump (302) and the tank (304) via fluid. The leg assembly (128, 130) comprises an actuator (206) that defines a rod end (210) and a head end (208). The hydraulic system (300) also comprises a first valve (308) that is arranged upstream of the head end (208) of the actuator (206). The first valve (308) is arranged via the main control valve (306) in selective fluid connection to the pump (302). The hydraulic system (300) further comprises a second valve (310) located upstream of the rod end (210) of the actuator (206). The second valve (310) is selectively connected to the pump (302) via the main control valve (306) and/or the reservoir (304). The second valve (310) selectively controls a fluid flow from the reservoir (304) and/or the pump (302) to the rod end (210) of the actuator (206) in order to retract the actuator (206).

Inventors

  • Nicholas James Argenziano
  • Eric Engelmann

Assignees

  • CATERPILLAR PAVING PRODUCTS INC.

Dates

Publication Date
20260513
Application Date
20251107
Priority Date
20241113

Claims (7)

  1. Hydraulic system (300) for a leg assembly (128, 130) of a working machine (100), wherein the leg assembly (128, 130) comprises an actuator (206) designed to retract in order to move the leg assembly (128, 130) from an extended state to a retracted state, the actuator (206) defining a rod end (210) and a head end (208), wherein the hydraulic system (300) comprises: a pump (302); a tank (304) designed to store fluid; a main control valve (306) designed to be in selective fluid connection with the pump (302) and the tank (304); a first valve (308) arranged upstream of the head end (208) of the actuator (206), wherein the first valve (308) is designed to be arranged in selective fluid connection with the pump (302) via the main control valve (306); and a second valve (310) arranged upstream of the rod end (210) of the actuator (206), wherein the second valve (310) is designed to be arranged in selective fluid connection with at least one of the pumps (302) and the tank (304) via the main control valve (306), and wherein the second valve (310) is designed to selectively control a fluid flow from at least one of the tanks (304) and the pump (302) towards the rod end (210) of the actuator (206) in order to retract the actuator (206).
  2. Hydraulic system (300) according to Claim 1 , which further comprises a control unit (312) which is connected to the main control valve (306) and the second valve (310).
  3. Hydraulic system (300) according to Claim 2 , wherein the working machine (100) further comprises a plurality of ground engagement elements (116, 117) designed to move between a lowered position and a raised position, wherein the first valve (308) is designed to receive a pilot fluid flow (F1) from the pump (302) via the main control valve (306) to actuate the first valve (308), wherein 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 bottom engagement element (116, 117) from the plurality of bottom engagement elements (116, 117) from the lowered position to the raised position and to lower a working tool (118) of the working machine (100) into a working surface (106).
  4. Hydraulic system (300) according to Claim 3 , wherein the control unit (312) is configured to control the main control valve (306) and the second valve (310) so that the fluid can flow from the pump (302) to the rod end (210) of the actuator (206) via the main control valve (306) to move the corresponding bottom engagement element (116, 117) from the plurality of bottom engagement elements (116, 117) from the lowered position to the raised position.
  5. Hydraulic system (300) according to Claim 2 , wherein the first valve (308) is designed to receive a pilot fluid flow (F1) from the pump (302) via the main control valve (306) to actuate the first valve (308), wherein actuation of the first valve (308) causes fluid to flow from the head end (208) of the actuator (206) towards the tank (304), and wherein the fluid flow from the head end (208) to the tank (304) causes the actuator (206) to retract due to at least one of the two forces, gravity and machine weight, to lower a working tool (118) of the working machine (100) into a working surface (106).
  6. Hydraulic system (300) according to Claim 5 , wherein the control unit (312) is configured to control the second valve (310) so that the fluid can flow from the tank (304) to the rod end (210) of the actuator (206) to retract the actuator (206), and wherein the fluid flow to the rod end (210) of the actuator (206) compensates for a volume change within a cylinder (212) of the actuator (206) during the retraction of the actuator (206).
  7. Hydraulic system (300) according to Claim 1 , where both the first valve (308) and the second valve (310) are balancing valves.

Description

Technical field The present disclosure relates to a working machine, in particular a hydraulic system for a leg assembly of the working machine and a method for controlling a movement of the leg assembly of the working machine. State of the art A machine, such as a cold milling machine or a recycler, is frequently used for milling, recycling, or stabilizing various surfaces, such as roads, highways, airport runways, and the like. The machine comprises a series of soil-working elements that can be raised or lowered as needed. It also includes a rotor that comes into contact with the work surface to perform operations. Furthermore, the machine includes several leg assemblies. These leg assemblies are movable between an extended and a retracted position to raise or lower the soil-working elements and/or the rotor. Typically, when retracted, the leg assemblies lower the working machine and rotor to achieve a desired cutting depth in a work surface. Each leg assembly includes an actuator that is pressurized with hydraulic fluid to move the corresponding leg assembly from the extended to the retracted position. However, if the rotor does not cut into the work surface to the desired depth, the leg assemblies may retract into the air. In such cases, the leg assemblies and/or the ground engagement elements may lift off the work surface, potentially compromising the stability of the working machine. Furthermore, in some cases, the rotor may continue cutting into the work surface before the lifted leg assemblies and/or the ground engagement elements make contact with it, which can result in undesirable depressions in the work surface. US Patent No. 3,888,542 describes a device for processing road surfaces, comprising a body with road wheels and carrying a cutting roller rotatably mounted about an axis transverse to the direction of travel and capable of being brought into contact with a road surface to remove a layer of the surface, containing a first hydrostatic pump connected to a hydrostatic motor for driving the roller, containing a second hydrostatic pump connected to a hydrostatic motor for driving at least one of the road wheels, and containing means for driving both pumps at a constant speed, wherein both pumps have continuously variable displacements and means for individually varying the displacements of the pumps are provided, thereby enabling any combination of roller and road wheel speeds. Summary of Disclosure In one aspect of the present disclosure, a hydraulic system for a leg assembly of a working machine is provided. The leg assembly includes an actuator designed to retract in order 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 designed to store fluid. The hydraulic system further includes a main control valve designed to be in selective fluid communication with the pump and the tank. The hydraulic system includes a first valve located upstream of the head end of the actuator. The first valve is designed to be in selective fluid communication with the pump via the main control valve. The hydraulic system also includes a second valve located upstream of the rod end of the actuator. The second valve is designed to be in selective fluid communication with at least one of the following: the pump via the main control valve and the tank. The second valve is designed to selectively control a fluid flow from at least one of the following elements: the tank and the pump towards the rod end of the actuator, in order to retract the actuator. In another aspect of the present disclosure, a working machine is provided. The working machine comprises a frame. The working machine also comprises at least two soil-engaging elements that are movable between a lowered position and a raised position. The working machine further comprises at least two leg assemblies. Each of the at least two soil-engaging elements is movable by means of a corresponding leg assembly from the at least two leg assemblies. Each of the at least two leg assemblies comprises a first tube. Each of the at least two leg assemblies also comprises a second tube, which The leg assembly is arranged within the first tube and is movable relative to the first tube. Each of the at least two leg assemblies also includes an actuator designed to retract in order 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 designed for storing fluid. The hydraulic system further includes a master control valve designed to be in selective fluid communication with the pump and the tank. The hydraulic system includes a first valve located upstream of the head end of t