Reversible Force Limiting Device for Medical Instruments
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Solution Overview
Problem
Existing medical instruments with force limiting devices often require disassembly for repair after exceeding a limit load, which is inconvenient for immediate reuse.
Innovation Solution
A force limiting device with two displaceable sleeve-shaped components and a ball-shaped force transmission element, where inclined contact surfaces trigger a sudden drop in force when the limit load is exceeded, allowing for tactile, acoustic, and visual feedback, and adjustable via a spring element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a predetermined breaking point is used for force limitation, then reliable protection of the instrument is ensured, but the instrument cannot be used again immediately because it has to be dismantled to repair the breaking point
Solution Approach 1:
The patent changes the physical state of the force limiting mechanism from a permanent breaking point to a reversible elastic deformation system. The tension/compression element is designed to deform elastically when the limit load is exceeded, then automatically return to its original state, enabling the instrument to be reused immediately without disassembly or repair.
2Ease of operation
If the force limiting device uses an elastically deformable part of the tension/compression element, then the instrument can be reused, but the reduction in force exerted is not clearly noticeable
Solution Approach 1:
The patent introduces a separate spring element as an intermediary component that works in conjunction with the tension/compression element. When the limit load is exceeded, the spring element compresses and provides a distinct tactile and acoustic signal (clicking sound), making the force reduction clearly noticeable to the user while maintaining the reversible nature of the force limiting device.
3Reliability
If the force limiting device is arranged in the shaft area, then it protects the instrument, but there is insufficient space due to the slim design of the shafts
Solution Approach 1:
The patent segments the medical instrument into distinct functional areas: the slim shaft for minimally invasive access and the handle area for housing larger components. The force limiting device is specifically located in the handle area where sufficient space is available, separating it from the constrained shaft environment while still providing protection for the entire instrument.
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
Enables a clear and immediate reduction in force exerted on the instrument, providing reversible protection without the need for disassembly, ensuring the device can be reused promptly and safely.
Implementation Method 1
the force limitation is designed as an elastically deformable part of the tension/compression element, which deforms reversibly when the limit load is exceeded
Implementation Method 2
the contact surfaces on which the at least one force transmission element rests on the two components are designed as inclined surfaces inclined towards one another
Data Source
Figure 1
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AI summary
The medical instrument (1) has a tool including a movable jaw part and arranged at a distal end of a hollow shaft (2). A handle (3) provided with a movable grip part (3b) is arranged at a proximal end of the shaft. Fixed and movable components (10, 12) are arranged in a housing (9) of a force limiting device (8) such that the fixed component is supported in the housing and the movable component is axially displaceable in the housing against force of a spring element (11). The components are coupled with each other over a force transmitting element (13) e.g. ball.