Injection Device With Rotating Driveshaft For High-Viscosity Medicament Delivery
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Solution Overview
Problem
Auto-injectors face challenges in delivering medicaments with high viscosity due to increased force requirements, which can lead to component failure and user discomfort, as existing solutions either require larger springs or increased needle diameter/time, both of which are undesirable.
Innovation Solution
The injection device employs an advancing mechanism and a stopper drive arrangement with a rotating driveshaft and a power spring, allowing independent control of needle insertion and medicament delivery forces, minimizing impact on the device and user comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a higher-force compression spring is used to drive the plunger for injection of high-viscosity drugs, then the injection force is improved, but the device length and stress on components increase
Solution Approach 1:
The patent divides the single plunger function into two separate mechanisms: an advancing mechanism for needle insertion and a stopper drive arrangement for medicament delivery. This segmentation allows each mechanism to be optimized independently, with the stopper drive using a compact power spring that can generate high forces without requiring excessive length, as it only needs to operate during the injection phase rather than the entire device assembly.
Solution Approach 2:
The patent transitions from a static compression spring system to a dynamic power spring system with a rotating driveshaft. The power spring stores energy in a compact form and releases it through rotational motion, allowing high force generation in a smaller volume. The clutch member enables dynamic engagement and disengagement, allowing the system to switch between storage and delivery phases efficiently.
2Force
If a higher-force compression spring is used to drive the plunger, then the injection force is improved, but the stress on plastic components and impact forces increase
Solution Approach 1:
The patent employs a power spring that stores energy gradually and releases it in a controlled manner through rotational motion of the driveshaft. This dynamic energy release mechanism reduces peak impact forces compared to a compression spring that would release energy linearly. The clutch member further controls the timing and magnitude of force transmission, protecting plastic components from excessive stress while ensuring sufficient injection force.
Solution Approach 2:
The power spring mechanism operates in periodic cycles: energy is wound into the spring during the retracted phase, then released during the injection phase. This periodic action allows the system to build up energy slowly and release it in a controlled burst, reducing overall stress on components while maintaining high injection force when needed.
3Force
If the needle diameter is increased to reduce injection resistance, then the injection of high-viscosity drugs is improved, but the needle visibility and precision are reduced
Solution Approach 1:
By separating the needle insertion function from the medicament delivery function, the patent allows the needle to be optimized for precision and small diameter (aided by the dedicated advancing mechanism), while the stopper drive arrangement compensates for high viscosity through controlled high-force application during the injection phase, eliminating the need to increase needle diameter.
4Force
If the injection time is increased to reduce injection force requirements, then the injection of high-viscosity drugs is improved, but the productivity is reduced
Solution Approach 1:
The power spring mechanism enables rapid energy release during the injection phase, allowing high-force delivery over a short time period. The periodic storage and release of energy in the power spring creates a high-speed injection action that maintains productivity while delivering sufficient force for high-viscosity drugs.
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 the efficient delivery of high-viscosity medicaments without compromising device reliability or patient comfort by separating the forces for needle insertion and medicament delivery, using a compact power spring to apply high forces to the stopper.
Implementation Method 1
the advancing mechanism comprises an insertion spring for axially moving the container and the stopper drive arrangement in the distal direction relative to the housing
Implementation Method 2
a drive spring housed in the drive body and biased for rotating the driveshaft
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(b)
AI summary
An injection device (100) suitable for the delivery of a viscous medicament from a container (10) through a needle (16) disposed at the distal end of the container (10) is disclosed. The device comprises a housing (102), an advancing mechanism (190, 204, 230) operable to move the container (10) relative to the housing from a starting position in which the needle (16) is shrouded and an insertion position in which the needle (16) is exposed, and a stopper drive arrangement operable to move a stopper (22) towards the distal end of the container (10). The stopper drive arrangement comprises a drive body (240) arranged for axial movement with respect to the housing (102), a driveshaft (250) arranged for rotation with respect to the drive body (240), a plunger (202) arranged for axial movement with respect to the drive body (240) to move the stopper (22) upon rotation of the driveshaft (250), and drive means (290) arranged to rotate the driveshaft (250) upon activation of the stopper drive arrangement.