Spindle Drive Catch Nut Safety Mechanism
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Solution Overview
Problem
Spindle drives in medical and industrial applications can experience unidentified wear or mechanical failure, leading to safety risks due to the loss of connection between the spindle and the mass being moved, especially in vertical configurations where failure results in uncontrolled movement or falling of heavy loads, and existing safety mechanisms like catch nuts are not easily detectable for rotating spindle nuts.
Innovation Solution
A spindle drive system with a catch nut that is initially not in mutual engagement with the spindle but moves into engagement upon spindle nut failure, featuring a switching element connected to an emergency off switch that is activated by axial movement of the spindle, allowing for automatic shutdown of the drive in case of failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catch nut is used as a safety mechanism in a rotating spindle nut system, then safety is improved by providing a backup connection, but detecting the engagement status becomes more difficult due to the rotating motion
Solution Approach 1:
The patent replaces electrical detection methods with a mechanical detection system. A mechanical sensor detects the axial position of the catch nut relative to the spindle nut through direct mechanical contact, avoiding the complexity of electrical contacts in rotating systems. This mechanical substitution resolves the detection difficulty while maintaining safety functionality.
Solution Approach 2:
The patent introduces a mechanical sensor as an intermediary element between the catch nut and the control system. This sensor translates the axial position of the catch nut into a detectable signal without requiring direct electrical contacts between rotating parts, thus solving the detection problem in rotating spindle nut systems.
2Measurement precision
If electrical contact methods are used to detect spindle nut and catch nut engagement, then detection is possible, but wear and errors increase due to contact degradation
Solution Approach 1:
The patent replaces electrical contact detection with a mechanical detection system using a sensor that detects axial position through mechanical means. This eliminates wear and error issues associated with electrical sliding contacts while maintaining detection precision.
3Reliability
If the catch nut is positioned close to the spindle nut for immediate engagement, then safety response time is improved, but the risk of unintended engagement increases
Solution Approach 1:
The patent applies different functional qualities to different parts of the system. The catch nut is positioned at a controlled distance from the spindle nut, with its engagement surface specifically oriented and positioned to ensure engagement only under failure conditions. This local differentiation of engagement conditions prevents unintended engagement while maintaining safety response.
Solution Approach 2:
The patent designs the catch nut and spindle nut with specific geometric features that prevent engagement under normal operating conditions. The engagement surfaces are oriented such that only axial displacement due to spindle failure can cause the catch nut to engage, creating a preliminary barrier against unintended engagement while maintaining readiness for safety intervention.
Data Source
AI summary
A spindle drive and patient positioning system is provided. The spindle drive includes a drive that is operative to drive a spindle nut. An axially transportable spindle is circled by the spindle nut. A catch nut that is not in mutual engagement with the spindle has a predefined distance to the drive. When the spindle nut fails, the spindle is operative to move the catch nut into mutual engagement with the spindle. A switching element is fixed to the catch nut and includes an emergency off switch, which is activated by a switching sensor.