Forklift Lift Valve Assembly for High-Speed Safe Lowering
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Solution Overview
Problem
Existing industrial trucks face limitations in achieving lifting and lowering speeds of ≥1 m/s while ensuring safe operations and compliance with safety regulations, particularly due to the activation of pipe rupture protection devices that limit speeds to between 0.6 m/s and 0.9 m/s.
Innovation Solution
A valve device with a fluid-controlled lifting and lowering stage and an electrically controllable pilot valve is interposed between the hydraulic lifting cylinder and the hydraulic system, allowing for controlled pressure adjustments to manage the lifting and lowering processes, eliminating the need for separate pipe rupture protection devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pipe rupture protection devices are used to ensure safe operation, then safety is improved, but lowering speed is limited to between 0.6 m/s and 0.9 m/s
Solution Approach 1:
The invention extracts and eliminates the pipe rupture protection device from the hydraulic system. By removing this safety device that limits lowering speed, the system achieves higher operating speeds (≥1 m/s) while maintaining safety through alternative means - specifically through controlled pressure reduction using the pilot valve and flow control stages that prevent shocks and uncontrolled movements without imposing speed restrictions
Solution Approach 2:
The invention changes the pressure parameter dynamically during the lowering process. The pilot valve reduces control pressure in a controlled manner before the lifting cylinder reaches its end position, which in turn reduces the load pressure and slows down the lowering speed at the appropriate moment. This parameter-based control achieves both high operating speeds and safe operation without mechanical speed limiting devices
2Productivity
If lowering speed is increased to ≥1 m/s to improve throughput, then productivity is improved, but safety risks increase due to potential shocks and uncontrolled movements
Solution Approach 1:
The invention performs preliminary action by reducing the control pressure through the pilot valve before the lifting cylinder reaches its end position. This advance pressure reduction causes a corresponding reduction in load pressure that smoothly decelerates the lowering process, preventing shocks and uncontrolled movements. The position sensor triggers this preliminary pressure reduction at an optimal moment, allowing high speeds during most of the stroke while ensuring safe deceleration near the endpoint
Solution Approach 2:
The invention implements feedback control through a position sensor that monitors the lifting cylinder's position and a control unit that adjusts the pilot valve accordingly. The sensor provides real-time position information, and the control unit responds by adjusting the control pressure to maintain safe operation. This closed-loop feedback system enables high productivity while preventing safety issues by continuously adapting the pressure and speed based on actual cylinder position
3Speed
If load pressure is reduced to enable high lowering speeds, then speed is improved, but control precision over the lifting process is worsened
Solution Approach 1:
The invention applies dynamics by making the control pressure variable rather than constant. The pilot valve dynamically adjusts the control pressure based on the cylinder position and operational requirements. During the majority of the stroke, high pressure enables fast lowering (≥1 m/s), while near the end position, the pressure is reduced to enable precise control and smooth deceleration. This dynamic pressure adjustment maintains both high speed and precise control at different phases of the operation
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 lifting and lowering speeds of ≥1 m/s with smooth transitions and minimal hydraulic losses, ensuring safe operations by preventing shocks and uncontrolled movements, and enhancing throughput.
Implementation Method 1
The valve device comprises a fluid-controlled lifting stage (12) and a fluid-controlled lowering stage (13)... an electrically controllable pilot valve (14) that is fluidly connected to a control port (12.3, 13.3) of the lifting stage (12) and a control port (12.3, 13.3) of the lowering stage (13)... the pilot valve (14) is designed and controllable in such a way as to increase a control pressure by a predefinable pressure value
Implementation Method 2
The valve device (11) is designed to be interposed between the hydraulic lifting cylinder (9) and the hydraulic system (10) for supplying the hydraulic lifting cylinder (9) with hydraulic fluid
Implementation Method 3
Enables lifting and lowering speeds of ≥1 m/s with smooth transitions and minimal hydraulic losses, ensuring safe operations by preventing shocks and uncontrolled movements
Data Source
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AI summary
The present invention relates to a valve assembly (11) for a forklift truck (1). The valve assembly (11) is designed to be interposed between a hydraulic lifting cylinder (9) and a hydraulic system (10) of the forklift truck (1). The valve assembly (11) comprises a lifting stage (12) and a lowering stage (13), wherein the lifting stage (12) and the lowering stage (13) each comprise a working port (12.1, 12.2, 13.1, 13.2) that is fluidically connected to the hydraulic system (10) and to the hydraulic lifting cylinder (9), respectively. The valve assembly (11) is characterized in that it comprises an electrically controllable pilot valve (14) that is fluidly connected to a control port (12.3) of the lifting stage (12) and a control port (13.3) of the lowering stage (13).The pilot valve (14) is designed and controllable in such a way as to increase a control pressure for controlling the lifting stage (12) and the lowering stage (13) during a lifting operation or during a lowering operation of the hydraulic lifting cylinder (9) before reaching an end position of the hydraulic lifting cylinder (9) by a predefinable pressure value.