Electro-Hydraulic Actuator Feedback Valve to Reduce Cam Wear
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Solution Overview
Problem
Electro-hydraulic actuators with mechanical feedback experience significant wear of components, particularly the cam, leading to a loss of functionality and increased maintenance costs due to relative movement between the cam and tappet.
Innovation Solution
Incorporating a ball that can be partially inserted into a connection duct with a spring to counteract the solenoid's thrust and reduce friction, along with a frusto-conical recess for improved stability and a magnetic body to facilitate fluid passage, which reduces wear and enhances the actuator's operational lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tappet and cam mechanism is used for mechanical feedback, then the actuator can achieve precise control and mechanical feedback functionality, but significant wear occurs on the cam and tappet components leading to reduced reliability and increased maintenance needs
Solution Approach 1:
The patent replaces the mechanical tappet-cam feedback mechanism with a magnetic field-based feedback system. A magnet is mounted on the piston and interacts with a reed switch or Hall sensor on the valve spool, eliminating direct mechanical contact between feedback components. This substitution maintains precise control functionality while eliminating wear, thereby resolving the contradiction between measurement precision and reliability.
2Ease of operation
If a tappet with rounded end and spring are used between the cam and slider, then the slider can be actuated proportionally with the stem translation, but the relative movement causes significant wearing of the cam and tappet components
Solution Approach 1:
The patent eliminates the mechanical tappet-cam actuation system by using a magnetic coupling between the piston and valve spool. The magnet on the piston directly actuates the valve spool through magnetic attraction, removing the intermediate tappet and cam components that caused wear. This maintains ease of operation while significantly extending component lifespan.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the piston and valve spool. Instead of direct mechanical contact through tappet and cam, the magnetic field transmits the actuation force, eliminating physical wear while maintaining the proportional actuation function. This intermediary approach resolves the contradiction between ease of operation and component durability.
3Manufacturing precision
If the cam is configured to cause proportional translation of the tappet, then the slider movement can be precisely controlled, but the relative movement between cam and tappet leads to alteration of the law of motion over time
Solution Approach 1:
The patent replaces the mechanical cam profile that defined the motion law with a magnetic field interaction. The magnet on the piston creates a magnetic force that directly controls the valve spool position without mechanical wear. This eliminates the gradual alteration of motion characteristics over time, maintaining both manufacturing precision and motion law stability.
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
The solution significantly reduces wear on the cam, prolongs the actuator's useful life, and decreases maintenance costs by minimizing friction and ensuring stable operation even when springs fail, thus maintaining precise control over the actuator's movement.
Implementation Method 1
a spring (195) arranged between the slider (135) and the ball (190) to counteract the thrust generated by the solenoid (180) and keep said ball (190) pressed on the cam (60)
Implementation Method 2
a solenoid (180) configured to generate a thrust adapted to actuate the slider (135)
Implementation Method 3
The translation of the tappet towards the slider causes a progressive increase of the preload of the spring arranged between the two, which progressively counteracts and subsequently overcomes the thrust exerted by the solenoid
Data Source
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AI summary
Electro-hydraulic actuator (10) comprising: a hydraulic cylinder (15) equipped with: a cylinder (20), a piston (25) slidably received in the cylinder (20) and adapted to divide the internal volume of the cylinder (20) into a first chamber (30) and a second chamber (35), a stem (40) connected to the piston (25) and passing outside of the cylinder (20), and a cam (60, 60a) associated with a portion of the stem (40) contained in the first chamber (30) of the cylinder (20), a hydraulic valve (80, 80a) equipped with: a valve body (85) coupled with the cylinder (20), a first access mouth (115) formed in the valve body (85) and placed in communication with the first chamber (30) through a connection duct (120, 120a) formed in the hydraulic cylinder (15), a second access mouth (125) formed in the valve body (85) and adapted to be placed in communication with a pump (P), and a third access mouth (130) formed in the valve body (85) and adapted to be placed in communication with a tank (T), a slider (135) received in the valve body (85) and slidable from a first position, wherein the slider (135) closes the second access mouth (125) leaving the third access mouth (130) in communication with the first access mouth (115), towards a second position, wherein the slider (135) closes the third access mouth (130) leaving the second access mouth (125) in communication with the first access mouth (115), passing from an intermediate position, wherein the slider (135) closes the second access mouth (125) and the third access mouth (130), and a solenoid (180) configured to generate a thrust adapted to actuate the slider (135), characterised in that it comprises a ball (190, 190a) at least partially inserted in the connection duct (120, 120a) and a spring (195, 195a), which is arranged between the slider (135) and the ball (190, 190a) to counteract the thrust generated by the solenoid (180) and keep said ball (190, 190a) pressed on the cam (60, 60a).