Sliding Measuring Instrument Lock Using Hard-Soft Friction
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Solution Overview
Problem
Existing femoral sizing guides used in orthopaedic surgery, particularly in knee replacement, face challenges in locking parts against relative movement, especially in fluid-filled wounds, where friction-based locking mechanisms like threaded knobs are cumbersome and difficult to use, and may not provide sufficient friction without mechanical advantage.
Innovation Solution
An apparatus utilizing a hard portion and a compressible portion with differing Shore hardness values, where the hard portion compresses the softer material to create friction and lock the parts, eliminating the need for threaded bores and knobs, allowing for fine adjustment and secure locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a threaded knob is used to lock the parts, then the locking reliability is improved, but the ease of operation deteriorates due to cumulative rounding error and difficulty of use with gloved hands
Solution Approach 1:
The patent replaces the threaded mechanical locking system with a friction-based locking system using a locking bar and friction surface. This substitution eliminates the cumulative rounding error inherent in threaded knobs while providing sufficient locking force through friction between the locking bar and the friction surface, improving both reliability and ease of operation with gloved hands.
Solution Approach 2:
The patent employs a disposable measuring instrument where the locking mechanism uses simple friction-based components rather than precision threaded fasteners. This approach accepts reduced mechanical complexity in exchange for improved ease of use and eliminates the need for high-precision reusable locking components.
2Ease of operation
If a friction-based locking system is used, then the ease of operation is improved, but the locking reliability deteriorates due to insufficient friction
Solution Approach 1:
The patent applies local quality by creating a specific friction interface between the locking bar and friction surface with optimized geometry and material properties. The friction surface is specifically designed with increased surface area and appropriate roughness to generate sufficient friction force at the local contact point, ensuring reliable locking while maintaining ease of operation.
3Strength
If metal components are used throughout, then the strength is improved, but the ease of operation deteriorates due to lack of compression and deformation
Solution Approach 1:
The patent uses composite materials combining metal components with plastic or elastomeric materials. The locking bar may be metal for strength, while the friction surface uses plastic or elastomeric material to provide compressibility and friction. This composite approach maintains structural strength while enabling easy compression and deformation for straightforward locking operation with gloved hands.
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 solution enables easy and secure locking of sliding parts in the apparatus, facilitating precise measurements and positioning during surgery, even with gloved hands, while minimizing the risk of debris and allowing for potential reusability or disposability.
Implementation Method 1
The differing material properties of the harder part and the compressible part allow the locking to be achieved more easily and enable the apparatus to be locked without requiring a threaded bore and corresponding threaded knob
Implementation Method 2
when the locking member is in the second position the compressible portion is at least partially compressed by the hard portion thereby preventing relative movement of the first and second parts
Data Source
AI summary
An apparatus and measuring instrument (2) comprise a first part and a second part configured for sliding movement relative to each other. The first part (9) comprises a locking member (20) comprising a hard portion (22) movable from a first position to a second position. The second part (6) comprises a compressible portion (18) which has a Shore hardness less than the hard portion and is positioned such that when the locking member is in the first position the compressible portion is not engaged by the hard portion, and when the locking member is in the second position the compressible portion is at least partially compressed by the hard portion thereby preventing relative movement of the first and second parts, hi an alternate embodiment the first part may comprise the compressible portion (34) and the second part may comprise the hard portion (38). The compressible portion has a Shore hardness less than the hard portion, so in the second position the compressible portion compresses or deforms around the hard portion. This compression creates friction to lock the relative position of the first and second parts with a fine level of adjustment.