Stack Valve Hydraulic Circuit for Independent Actuator Control
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Solution Overview
Problem
Existing stack valves in construction machines are inefficient as they require the service valve to be returned to neutral position for the boom and bucket to become movable again after being stopped due to physical contact or overload, leading to poor operationality.
Innovation Solution
A stack valve design with multiple serially-connected direction switching valves and a hydraulic circuit that allows pressure fluid to return to the tank when an actuator is stopped, enabling operation of connected actuators without returning the direction switching valve to neutral, using unloading and tank paths, supply and discharge paths, and a splitter to manage fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the service valve is operated to activate an attachment connected via an actuator, then the attachment can perform work, but when the attachment is stopped due to physical contact or overload, the boom and bucket become immobile until the service valve is returned to neutral position
Solution Approach 1:
The hydraulic system is segmented into multiple independent control paths. The service valve controls the attachment actuator independently from the boom and bucket actuators. When the attachment stops due to overload, the hydraulic fluid can bypass through alternative paths (unloading path or tank return path) allowing boom and bucket operations to continue independently without requiring the service valve to be returned to neutral position.
2Productivity
If the service valve remains in the operated position after attachment stops, then the attachment remains stopped, but the boom and bucket cannot be operated until the valve is returned to neutral
Solution Approach 1:
An intermediary hydraulic path is introduced between the service valve and the boom/bucket actuators. This intermediary path includes the unloading path and tank return path that can carry hydraulic fluid even when the service valve is in the operated position. This intermediary mechanism allows the hydraulic system to maintain flow to boom and bucket actuators independently of the service valve position, enabling continuous operation.
3Adaptability or versatility
If a traditional stack valve configuration is used, then the structure is simple, but the operational flexibility is limited when downstream actuators are stopped
Solution Approach 1:
The unloading path and tank return path serve multiple functions within the hydraulic system. These paths can handle return fluid from any actuator in the system, not just the attachment actuator controlled by the service valve. This multi-functional design allows any actuator to operate independently even when other actuators are stopped, providing universal operational flexibility across the entire hydraulic system without requiring complex individual control mechanisms for each actuator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the actuator connected to the upstream direction switching valve to remain operable even when the downstream actuator is stopped due to overload, improving operational efficiency by allowing fluid flow through the system without requiring the service valve to be returned to neutral.
Implementation Method 1
a hydraulic pump 2 and a stack valve 1 having a boom direction switching valve 11, a bucket direction switching valve 12 and a service valve 13 connected in this order in series on a pressure fluid supply side
Implementation Method 2
the pressure fluid returns from the first supply and discharge paths to the unloading path when the first actuator is activated
Data Source
AI summary
A stack valve 1 includes a boom direction switching valve 11 (first direction switching valve) connected to an unloading path 21 and a service valve 13 (second direction switching valve) connected to the unloading path 21 at the downstream of the boom direction switching valve 11. At changeover positions 11a and 11c at which the unloading path 21 on the upstream side is connected to one of the supply and discharge paths 29 and 30 and the other one of the supply and discharge paths 29 and 30 is connected to the unloading path 21 on the downstream side, the boom direction switching valve 11 is connected to a boom valve tank return path 27 which connects the other one of the supply and discharge paths 29 and 30 with the tank path 22.