Syringe Plunger Rod Lug Thread Engagement Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The force exerted by a resiliently deformable bung on the plunger rod in syringes can cause issues with full drug delivery, as it may push the plunger rod outwards, leading to inefficiencies in substance expulsion.
Innovation Solution
A plunger rod design featuring laterally extending lugs with thread engagement surfaces that engage with a track portion of the bung's thread, preventing the plunger rod from being forced outwards by managing the energy stored in the compressed bung, allowing it to remain under compression and redistribute energy to prevent outward movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resiliently deformable bung is used to ensure full drug delivery, then delivery completeness is improved, but the bung may force the plunger rod outwards causing delivery inefficiency
Solution Approach 1:
The bung is segmented into a resiliently deformable portion and a rigid thread portion. The resilient portion compresses to ensure complete drug delivery, while the rigid thread portion engages with the lug to prevent the plunger rod from being forced outward, thus resolving the contradiction between delivery completeness and expulsion efficiency.
Solution Approach 2:
Different portions of the bung have different mechanical properties: the main body is resiliently deformable to compress and push the plunger rod inward for complete delivery, while the thread portion is rigid to engage with the lug and prevent outward movement. This local differentiation of material properties resolves the technical contradiction.
2Strength
If the bung is allowed to expand under stored energy, then the plunger rod can be pushed outwards, but this causes unwanted movement and delivery inefficiency
Solution Approach 1:
The lug acts as an intermediary between the bung's thread portion and the plunger rod. It engages with the thread to convert the bung's expansion energy into rotational motion rather than allowing direct outward movement of the plunger rod, thus maintaining position stability while utilizing the elastic energy.
Solution Approach 2:
The expansion energy of the bung, which could harmfully push the plunger rod outward, is converted into beneficial rotational motion through thread engagement with the lug. This converts a potentially harmful effect into a useful function that maintains delivery efficiency.
3Ease of operation
If the plunger rod is freely movable, then it can respond to bung pressure, but it may be forced outwards by compressed bung energy
Solution Approach 1:
The lug-thread engagement mechanism provides a counteracting force to the outward expansion force of the bung. As the bung expands, the thread engagement with the lug creates an opposing force that prevents the plunger rod from being forced outward, balancing the forces acting on the system.
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
This design ensures consistent and efficient expulsion of substances from the syringe by maintaining bung compression and preventing unwanted outward movement of the plunger rod, enhancing the delivery mechanism.
Implementation Method 1
a resiliently deformable bung in compression in at the end of a barrel of the syringe... energy stored in the bung when it is compressed
Implementation Method 2
at least one laterally extending lug comprising a thread engagement surface configured to engage with a point on a track portion of a thread on a sidewall of the recess
Data Source
Figure 1a~1b
Figure 2
Figure 3~4
AI summary
A plunger rod for use in a syringe barrel for driving a bung through the syringe barrel to expel a substance therefrom, the plunger rod comprising: a bung fixing configured to be received within a recess of a bung and comprising at least one laterally extending lug comprising a thread engagement surface configured to engage with a point on a track portion of a thread on a sidewall of the recess, wherein the lug is further configured to cross the thread on relative rotation between the plunger rod and the bung under a force applied by a user, such that the thread engagement surface of the lug engages the point of the track portion every full rotation of the syringe plunger relative to the bung.