External Wire Encoder Mounting for Hydraulic Actuator Position Sensing
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Solution Overview
Problem
Existing hydraulic actuator systems require modification to accommodate position-sensing encoders, which increases complexity and cost, and existing solutions do not provide a straightforward method for determining the position of hydraulic actuators without altering the actuator's structure.
Innovation Solution
A wire actuated encoder is mounted externally on the hydraulic actuator cylinder, using a housing with a rotating drum and wire guides to ensure smooth wire movement, allowing for the determination of piston stroke without modifying the cylinder's length, and can be easily installed or retrofitted onto standard actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotary encoder is mounted inside the cylinder to measure piston stroke, then position measurement capability is improved, but the cylinder length must be increased to accommodate the encoder and associated apparatus
Solution Approach 1:
The encoder is relocated from the internal axial space to the external radial surface of the cylinder. The encoder housing is mounted on the outside of the cylinder wall, with the drum positioned laterally adjacent to the cylinder rather than inside it. This dimensional relocation eliminates the need to extend cylinder length while preserving position measurement functionality.
Solution Approach 2:
A wire acts as an intermediary element connecting the piston to the externally mounted encoder drum. The wire transmits the piston's linear motion to the drum, causing it to rotate proportionally to the piston stroke. This intermediary mechanism enables the external encoder to accurately measure internal piston position without direct internal mounting.
2Productivity
If an encoder is mounted on the cylinder to determine position, then productivity and safety are improved through better position detection, but device complexity increases due to modification requirements
Solution Approach 1:
The position sensing function is segmented from the hydraulic actuator system. The encoder is mounted as a separate, independently adjustable component on the cylinder exterior rather than being integrated into the actuator's internal structure. This segmentation reduces overall system complexity while enabling position measurement capabilities that improve productivity and safety.
Solution Approach 2:
The mounting position and orientation of the encoder can be adjusted to optimize performance for different application requirements. The encoder's location on the cylinder surface and the wire attachment point can be varied to achieve the desired measurement range and resolution, allowing flexibility in system design without increasing inherent complexity.
3Measurement precision
If the cylinder is modified to accommodate an internal encoder, then position measurement is enabled, but ease of manufacture and installation deteriorates due to structural modifications
Solution Approach 1:
The encoder assembly is extracted from the cylinder's internal structure and mounted on the external surface. This eliminates the need to modify the cylinder bore, piston rod, or internal components to accommodate the encoder. The cylinder can be manufactured using standard procedures without additional machining or structural changes, while the encoder is installed as a separate component.
4Reliability
If wire guides are added to ensure smooth wire running, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
Wire guides act as intermediary elements between the wire and the encoder drum. These guides ensure the wire runs smoothly and maintains proper alignment as it winds onto and off the drum, preventing binding, friction, or misalignment that would compromise measurement reliability. The guides are simple structural features integrated into the encoder housing rather than complex mechanisms.
Data Source
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AI summary
A hydraulic actuator with a sensor mounted on the actuator cylinder for determining the position of the actuator. The arrangement comprises a hydraulic actuator (16) which includes a cylinder (19) having a bore in which a piston (18) is slidably mounted for movement along the cylinder to extend and retract the hydraulic actuator. The cylinder has a side wall and a cylinder aperture (42) extending through the side wall. A wire actuated encoder (30) is mounted on the external surface (31) of the cylinder (19), which has a wire (36) which extends through the cylinder aperture (42) and is attached to the piston (18) for determining a stroke position of the piston within the cylinder.