Variable Piston Force Drug Delivery Drive Mechanism
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Solution Overview
Problem
Current drug delivery devices, particularly pen-type devices, lack the ability to efficiently manage variable doses, especially for users without formal medical training, such as diabetic patients, and often require higher forces for initial dispensing due to bung stiction, which can be challenging and inefficient.
Innovation Solution
A drug delivery device with a housing that houses a cartridge and a drive mechanism, featuring a bung that is movably retained within the cartridge, and a drive mechanism that adjusts the maximal driving force based on the bung's position and the cartridge's filling level, providing an initial higher force to overcome stiction and then reducing it for subsequent doses, utilizing a combination of energy storage and supplemental storage members to assist in dispensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a spring-driven mechanism is used to dispense drug doses, then the device can operate automatically without manual force application, but the initial stiction force required to move the bung from rest is excessively high, causing unreliable dose delivery
Solution Approach 1:
The patent applies dynamics by making the spring stiffness variable rather than constant. The spring mechanism transitions from a stiff initial state to a more compliant state as the bung moves, allowing high initial force to overcome stiction, then reducing force for the remainder of the stroke. This dynamic adjustment resolves the contradiction between automatic operation and excessive initial force requirements.
Solution Approach 2:
The patent changes the physical parameter of spring stiffness during operation. By using a progressive spring mechanism where the effective spring constant varies with displacement, the system provides high force when needed (at startup to overcome stiction) and lower force afterward. This parameter change directly addresses the force contradiction while maintaining automation.
2Reliability
If a high force is applied to overcome initial bung stiction, then the device can reliably start dispensing, but the excessive force causes discomfort and difficulty for users without medical training
Solution Approach 1:
The patent replaces the simple mechanical spring system with a progressive spring mechanism that intelligently modulates force output. This substitution maintains the mechanical advantage of spring-driven automation while eliminating the disadvantage of excessive user-applied force. The progressive spring automatically adjusts force levels, ensuring reliable Bung movement without requiring high user effort.
Solution Approach 2:
By implementing dynamic force adjustment through the progressive spring mechanism, the system delivers high force only when necessary (to overcome stiction) and reduces force afterward. This dynamic behavior resolves the contradiction between reliability (needing high initial force) and ease of operation (needing low user effort).
3Device complexity
If a fixed spring preload is used to drive the bung, then the device structure is simple, but the force applied to the bung cannot be adjusted for different filling levels, leading to inefficient dispensing
Solution Approach 1:
The patent implements parameter changes by making the spring stiffness variable rather than fixed. The progressive spring mechanism automatically adjusts the effective spring constant based on the bung position and cartridge filling level. This allows the system to optimize force application for different dosing scenarios without requiring complex external control systems, thus maintaining relatively simple structure while improving dispensing efficiency.
Solution Approach 2:
The progressive spring mechanism introduces dynamic adaptability to the drive system. Rather than a fixed preload, the spring characteristics change during operation to match the varying resistance encountered at different filling levels. This dynamic adjustment improves productivity by ensuring optimal force is applied throughout the dispensing process while keeping the overall device structure manageable.
4Device complexity
If manual force application is required to dispense each dose, then the device structure is simple, but users without medical training cannot reliably select and administer variable doses
Solution Approach 1:
The progressive spring mechanism enables self-service operation by automatically providing the necessary force variations throughout the dispensing process. Users simply need to initiate the process, and the system self-adjusts the force profile to overcome stiction and complete the dose delivery. This eliminates the need for users to manually manage complex force application while maintaining relatively simple device structure.
Solution Approach 2:
The patent replaces manual force management with an automated progressive spring mechanism. This substitution maintains mechanical simplicity while dramatically improving ease of operation for variable dose administration. Users no longer need to understand or control the force profile; the progressive spring handles this automatically, making the device accessible to non-medical users.
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 user-friendly, efficient dispensing of variable drug doses with reduced user effort and increased accuracy by adjusting the driving force according to the bung's position and cartridge filling level, effectively addressing the initial stiction challenge and ensuring consistent dispensing throughout the device's operation.
Implementation Method 1
devices which are driven by a spring or the like
Implementation Method 2
utilizing a combination of energy storage and supplemental storage members to assist in dispensing
Data Source
Figure 1~3
Figure 4a~5
Figure 6~8
AI summary
The present disclosure relates to a drug delivery device, comprising a housing (10), a cartridge (100), the cartridge containing a drug in a quantity sufficient for a plurality of doses of the drug, a bung (101 ), the bung being movably retained within the cartridge to dispense a dose of the drug from the cartridge upon movement of the bung with respect to the cartridge, and a drive mechanism (30), the drive mechanism being operable to transfer a driving force to the bung to dispense the dose of the drug from the cartridge, wherein the drug delivery device is configured such that the maximal driving force which is transferable to the bung via the drive mechanism varies and is adjusted to the current position of the bung within the cartridge.