Torque-Limiting Screw Element for Plastic Line Fastening
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Solution Overview
Problem
Existing screw elements used to fasten plastic lines in high-pressure applications, such as chromatography, often face challenges in reliable tightening without damaging the thread or seal, especially in tight spaces where accessibility is difficult and manual tightening may not ensure the correct torque.
Innovation Solution
A screw element with a torque limiting unit that includes a separate limiting element, assembled from connectable parts, which limits the axial torque transmission between the connection and actuation parts, preventing overtightening by disconnecting the axial connection when a predefined torque limit is exceeded, thus protecting against damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw element is tightened sufficiently to ensure secure connection, then the connection reliability is improved, but the thread or seal may be damaged due to excessive torque
Solution Approach 1:
The screw element incorporates an integrated torque limiting unit that automatically prevents overtightening. When the maximum safe torque is reached, the limiting element disengages from the connection part, causing the actuation part to rotate independently while the connection part remains stationary. This self-regulating mechanism ensures reliable connection without risking thread or seal damage.
Solution Approach 2:
The torque limiting unit allows the actuation part to rotate beyond the point where the connection part is fully secured. The limiting element is designed to disengage at a predetermined torque threshold, permitting partial rotation of the actuation part relative to the connection part. This ensures the connection is sufficiently tight while preventing excessive torque transmission that could cause damage.
2Ease of operation
If manual tightening is used for simplicity, then ease of operation is improved, but sufficient tightening may not be achieved in tight spaces
Solution Approach 1:
The torque limiting unit provides automatic torque control without requiring special tools or techniques. The limiting element's predetermined disengagement point ensures that sufficient tightening is always achieved, regardless of operator skill or accessibility conditions. Users can simply apply force to the actuation part, and the system self-regulates to achieve proper connection.
3Reliability
If a tool is used to ensure sufficient tightening, then tightening reliability is improved, but device complexity increases and special tools are required
Solution Approach 1:
The torque limiting unit integrates the torque control function directly into the screw element. The limiting element's design with predetermined disengagement characteristics automatically provides torque control, eliminating the need for external torque-limiting tools or specialized tightening equipment. The system serves itself by built-in mechanical feedback.
Solution Approach 2:
The screw element combines multiple functions: connection, torque transmission, and torque limitation. The actuation part can be operated with simple manual force or basic tools, while the integrated torque limiting unit ensures proper tightening without requiring specialized equipment. This multi-functional design simplifies the overall system.
4Ease of manufacture
If the screw element is made from plastic for simplicity, then ease of manufacture is improved, but the torque transmission capability is reduced
Solution Approach 1:
The screw element is divided into functionally distinct parts: the connection part with thread and limiting element that remains stationary during tightening, and the actuation part that rotates. This segmentation allows the connection part to be made from plastic with simplified manufacturing, while the actuation part transmits torque through a different mechanism (friction between limiting element and connection part) rather than relying solely on thread strength.
Data Source
AI summary
The invention relates to a screw element comprising an internal torque limitation for fastening a liquid-conducting line to a device connector or to a coupling for a further line, said screw element having a connection part, which preferably has a thread, and an actuation part; and having a torque limiting unit that limits a torque that can be transmitted from the actuation part to the connection part, wherein the torque limiting unit is arranged between the connection part and the actuation part and has a limiting element, in particular a separate limiting element, that can be assembled from at least two limiting element parts connectable to one another and that limits the torque limiting unit in an axial direction of a longitudinal axis of the screw element. The invention further relates to a system comprising at least one screw element and a line fastened to the screw element.