Catheter Assembly Locking Mechanism for Needle Protrusion Stability

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Solution Overview

Problem

Catheter assemblies with flexible catheters tend to shrink over time, leading to retraction of the distal end relative to the inner needle, causing increased protrusion of the inner needle and potentially deep punctures that may damage blood vessel walls during insertion.

Innovation Solution

A catheter assembly with an inner needle featuring a barrel, an inclined blade surface, and a locking surface that contacts a corresponding locking surface on the catheter, restricting relative movement and maintaining the inner needle's protrusion, even with catheter shrinkage, through a recessed intermediate surface and bulging portions for secure locking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a flexible catheter is used to facilitate insertion and placement, then the ease of operation is improved, but the catheter is liable to shrink over time causing retraction of the distal end relative to the inner needle

Engineering Contradiction:

Improveease of insertion and placementVSAvoiddimensional stability of catheter

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The locking surface is pre-formed on the inner needle at a predetermined position. Before any shrinkage or retraction can occur, this locking surface is already in place to engage with the catheter, preventing relative movement between the inner needle and catheter even as the catheter undergoes dimensional changes over time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The locking surface acts as an intermediary element between the inner needle and the catheter. It provides a mechanical interface that transfers and restrains relative movement, serving as a mediator that connects the two components while preventing the harmful retraction effect.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the catheter shrinks causing retraction of the distal end, then the stability is worsened, but the inner needle protrusion increases leading to potential deep puncture damage

Engineering Contradiction:

Improverelative position stabilityVSAvoidneedle protrusion and potential tissue damage

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The locking surface is designed to apply a preliminary counteracting force against the retraction tendency of the catheter. By engaging the locking surfaces before significant retraction occurs, the system prevents the development of excessive needle protrusion that would lead to harmful deep puncture damage.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The potential harm of catheter shrinkage is converted into a beneficial locking mechanism. The shrinkage force that would normally cause retraction and excessive needle protrusion is instead harnessed to press the locking surfaces together, creating a secure mechanical lock that prevents the harmful effect.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the locking surface is added to restrict relative movement, then the reliability is improved, but the device complexity increases

Engineering Contradiction:

Improverestriction of relative movementVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Rather than making the entire catheter or needle complex, the locking surface is applied locally at a specific position on the inner needle. This localized feature provides the necessary reliability for restricting relative movement while minimizing the overall device complexity by keeping the modification confined to a small, specific area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The locking surface is implemented as a simple, easily manufactured feature on a disposable medical device. The complexity is kept minimal and acceptable because the inner needle and catheter assembly is designed as a single-use disposable unit, where the added locking feature does not significantly increase manufacturing complexity or cost.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS10828466B2Catheter assembly

Publication Date: 2020.11.10 TERUMO KK

AI summary

A catheter assembly includes: a catheter having an inner cavity; and an inner needle retractably located in the inner cavity of the catheter. The inner needle includes: a barrel, a blade surface located distal of the barrel and being inclined with respect to a center axis of the inner needle, and an inner needle side locking surface located at least at a portion of an outer surface linking the barrel with the blade surface. An inner surface of the catheter includes a catheter side locking surface in contact with the inner needle side locking surface such that relative movement of the catheter in a proximal direction with respect to the inner needle is restricted.