Switch Unit Position Sensing for Hydraulic Drives
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Solution Overview
Problem
Existing position detection devices for hydraulic or electro-hydraulic drives, such as potentiometers, fail under extreme conditions like very low temperatures and explosion hazards, leading to inaccurate control and regulation of actuators.
Innovation Solution
A device using a switch unit with multiple switches and a rotary actuating element mechanically coupled to the drive shaft, providing quasi-continuous position detection through a unique combination of switching positions stored in a control module, eliminating the need for continuous electrical sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If potentiometers are used for continuous position detection, then measurement precision is improved, but reliability deteriorates under extreme conditions
Solution Approach 1:
The continuous position detection function is segmented into discrete switch states. Instead of using a single continuous sensor (potentiometer), the system divides the position range into multiple segments detected by separate switches. Each switch detects a specific position segment, and the combination of switch states encodes the overall position, achieving both precision and reliability.
Solution Approach 2:
The patent replaces the electrical continuous sensing mechanism (potentiometer) with a mechanical switching system. The rotary actuating element mechanically actuates switches at discrete positions, converting continuous mechanical motion into discrete electrical signals. This mechanical-to-electrical conversion approach improves reliability under extreme conditions while maintaining position detection precision.
2Reliability
If limit switches are used for end position detection, then reliability is improved, but measurement precision deteriorates due to loss of intermediate position information
Solution Approach 1:
The patent segments the position detection function across multiple switches arranged along the travel range. Instead of using a single limit switch for end positions, multiple switches are distributed throughout the travel range, each detecting its specific segment. This segmentation enables both reliable detection (each switch is simple and robust) and precise relative position information (the pattern of active switches encodes the exact position).
Solution Approach 2:
The patent transitions from detecting position in one dimension (end positions only) to detecting position across multiple dimensions by using multiple switches at different positions. The combination of switch states creates a multi-dimensional position encoding that provides both reliability and precision simultaneously.
3Measurement precision
If electrical sensors are used for position detection, then measurement precision is improved, but reliability deteriorates in explosion hazards and extreme temperatures
Solution Approach 1:
The patent replaces continuous electrical sensors with a mechanical switching system that has inherent safety features. The mechanical switches have no moving electrical contacts, and the system uses simple dry-contact switching that cannot generate sparks. This mechanical approach eliminates the electrical hazards associated with explosion risks while maintaining position detection capability.
Solution Approach 2:
The patent employs simple, inexpensive mechanical switches that can be easily replaced if needed, rather than relying on complex, expensive electrical sensors. These simple switches are inherently more resistant to environmental damage from extreme temperatures and explosion hazards, providing a more reliable and safer solution.
Data Source
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AI summary
The invention relates to a device (10) for sensing a rotary position or linear position of moving parts of drives, in particular of hydraulic or electrohydraulic drives, which are functionally reliable under extreme ambient conditions such as in very low temperatures or where there is a risk of explosion, in which a moving part (1) performs a rotary movement or a linear positioning movement with respect to a stationary part (2), said device having a switch unit (3), which comprises a plurality of switches (31, 32, 33, 34, 35) arranged next to one another in a row, the switch unit (3) being arranged on the stationary part (2), and having an actuation element (4) for directly or indirectly actuating the switches (31-35) of the switch unit (3) in accordance with the relative position of the moving part (1), the actuation element (4) having a plurality of switch triggers (41, 42, 43, 44, 45) corresponding to the number of switches (31-35) of the switch unit (3), and the switch triggers (41-45) each being assigned to the respective switches (31-35), by being lined up and/or arranged between the moving part (1) and the stationary part (2), such that there is a respectively defined unique combination of switch positions of the switches (31-35) for each relative position between the moving part (1) and the stationary part (2), and a control module having an analysis unit is provided, in which coding for the different switch positions of the switches (31-35) in relation to the relative position of the moving part (1) of the drive is stored.