Medical Instrument Force Limiting Device
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Solution Overview
Problem
Existing medical instruments with force limiting devices often require disassembly for repair after exceeding a limit load, and existing solutions either completely reduce force or do not maintain resistance force after triggering.
Innovation Solution
A force limiting device with axially displaceable components and a force transmission element, such as balls, that maintains a constant tensile force by increasing resistance through inclined contact surfaces and a spring-loaded mechanism, allowing continuous displacement without exceeding the limit load and enabling reversible operation.
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 force limiting device changes the physical state of the friction element from static friction (high friction coefficient) to kinetic friction (lower friction coefficient) when the limit load is exceeded. This parameter change allows the device to switch from a high-friction locking state to a low-friction sliding state, enabling automatic reset without disassembly while maintaining reliable force limitation
Solution Approach 2:
The friction element automatically resets itself by transitioning from a stuck state to a sliding state when the limit load is exceeded. The kinetic friction force is sufficient to maintain engagement during normal operation but allows automatic resetting when overloaded, eliminating the need for manual intervention or disassembly for repair
2Reliability
If the force limiting device reduces the force applied via the handle to zero when triggered, then the limit load is protected, but it is not possible to leave the force applied via the handle on the handle even after the limit load has been exceeded
Solution Approach 1:
The friction element dynamically adjusts its friction characteristics based on the applied load. During normal operation, static friction maintains a firm connection. When the limit load is exceeded, the element transitions to kinetic friction, allowing controlled sliding that maintains force transmission while preventing damage. This dynamic behavior enables continuous force application even after triggering
Solution Approach 2:
Instead of completely disengaging the force transmission when the limit load is exceeded, the device allows partial slippage through the kinetic friction mechanism. This partial action maintains enough force transmission to keep the handle engaged and operational, preventing complete force reduction to zero while still protecting from excessive loads
3Ease of repair
If an elastically deformable part of the tension/compression element is used for force limitation, then reversible operation is achieved, but the force applied via the handle is not maintained after triggering
Solution Approach 1:
The friction element acts as an intermediary between the handle and the jaw parts, providing a controllable interface that maintains force transmission. Through friction engagement, it allows the handle to remain engaged and maintain resistance force while still limiting the force transmitted to the jaw parts, serving as a mediator that preserves operational continuity
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
The device ensures the force applied to the handle remains constant beyond the limit load, preventing damage and allowing immediate reuse by maintaining resistance force, with visual indication of trigger activation.
Implementation Method 1
two components (10, 11) which can be displaced in opposite directions to one another in the longitudinal direction of the housing (9) are arranged in such a way that both components (10, 11) can be axially displaceable against the force of at least one spring element (12) arranged in the housing (9)
Implementation Method 2
at least one force transmission element (13) acting on both components (10, 11), which rests on contact surfaces (10a, 11a) of the two components (10, 11), on which the at least one force transmission element (13) rests on the two components (10, 11)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a medical instrument (1) with a shaft (2) at the distal end of which a tool (4) having at least one movable jaw part (4b) is arranged and at the proximal end of which a handle (3) provided with at least one movable grip part (3b) is arranged, wherein the movable jaw part (4b) and the movable grip part (3b) are operatively connected to each other via a pull/push element (6) and wherein at least one reversibly acting force limiting device (8) for limiting the force transmission from the movable grip part (3b) to the components (4b, 6) operatively connected to the movable grip part (3b) is arranged between the movable grip part (3b) and the movable jaw part (4b).In order to create a medical instrument (1) with a force limiting device (8) which ensures that the applied resistance force is maintained when the limit load is reached, it is proposed according to the invention that the force limiting device (8) comprises a housing (9) in which two components (10, 11) which are displaceable in opposite directions in the longitudinal direction of the housing (9) are arranged such that both components (10, 11) are axially displaceable in the housing (9) against the force of at least one spring element (12) arranged in the housing (9), wherein both components (10, 11) are coupled to each other via at least one force transmission element (13) acting on both components (10, 11).