Pilot-Controlled Proportional Valve for Electric Forklifts
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Solution Overview
Problem
Existing valve designs for hydraulic lifting devices, particularly in electric forklifts, face challenges in achieving high no-load lowering speed with minimal leakage and precise metering, as they require high control pressures which are not readily available without an external supply, leading to hampered lowering processes.
Innovation Solution
A pilot-controlled proportional seat valve or gate valve design that utilizes a cross-sectional constriction in the main piston and a pilot piston, actuated by a magnet means, allowing for low pilot pressure operation (<2 bars) and precise metering of lowering speed with minimal leakage, using a compression spring to adjust for flow forces and maintain valve position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pilot-controlled valves are used for high volumetric flow, then flow capacity is improved, but control pressure availability deteriorates (requires external supply not available in electric forklifts)
Solution Approach 1:
The patent replaces the conventional barometric pressure control system with an electromagnetic actuation system. A magnet means (electromagnet) directly actuates the pilot piston, eliminating the need for barometric pressure supply. This substitution allows the valve to be controlled electrically rather than hydraulically, solving the control pressure availability problem in electric forklifts while maintaining high flow capacity.
Solution Approach 2:
The patent changes the control mechanism from pressure-based (barometric) to electromagnetic force-based. By using a magnet means to generate electromagnetic force that directly moves the pilot piston, the system transforms the control parameter from hydraulic pressure to electromagnetic force, enabling operation without external pressure supply.
2Device complexity
If directly controlled valves are used, then device complexity is reduced, but flow capacity deteriorates (not suitable for high volumetric flow)
Solution Approach 1:
The valve is segmented into a main valve body for high flow capacity and a pilot control section for precise control. The pilot valve with its piston and magnet means is integrated into the main valve structure, allowing the system to achieve high volumetric flow through the main valve while maintaining relatively simple overall structure through functional integration.
Solution Approach 2:
The pilot control mechanism is nested within the main valve structure. The pilot piston and magnet means are integrated into the valve body, with the pilot control section embedded in the main valve assembly. This nesting allows the compact pilot control to be housed within the larger flow-capable valve body, achieving both high flow capacity and acceptable structural simplicity.
3Ease of manufacture
If conventional valve designs are used, then manufacturing cost is reduced, but lowering speed control precision deteriorates (cannot achieve precise metering)
Solution Approach 1:
The patent replaces conventional mechanical flow control mechanisms with an electromagnetic actuation system. The magnet means provides precise, proportional control of the pilot piston position based on current input, enabling accurate metering of lowering speed. This electromagnetic control offers superior precision compared to traditional mechanical adjustments while maintaining reasonable manufacturing complexity.
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 high no-load lowering speed with precise metering and low leakage, suitable for electric forklifts without the need for external pressure supply, improving operational reliability and efficiency.
Implementation Method 1
a magnet means which can carry current... can be actuated by a magnet means which can carry current
Implementation Method 2
a compression spring is configured between the main piston and the pilot piston
Implementation Method 3
the pilot control opened, fluid travels from one of the two ports which can be actuated by the main piston by a cross-sectional constriction in the main piston and the pilot control to the third port
Data Source
AI summary
A valve, in particular, a proportional seat valve or gate valve, includes a valve housing (10) and at least three fluid connections (1, 2, 3) extending through the valve housing. A main piston (18) extends in the valve housing (10). A pilot piston (24) for executing a pilot control (26) may be controlled by a current-carrying magnetic device (28). During an open pilot control (26), fluid from one (2) of the connectors (1, 2), controlled by the main piston (18), reaches the connector (3), controlled by the pilot piston (24), by a cross-sectional narrowing (38) in the main piston (19). The pilot control (26) and, as a result of the corresponding pressure drop, the main piston (18) achieves a control position, controlling both fluid connections (1, 2) with regard to fluid amount.