Two-Piece Piston Rod Delay Mechanism for Medical Dispensing
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Solution Overview
Problem
Existing medical delivery devices with delay mechanisms for insulin and hormone administration are costly to manufacture due to the difficulty and expense of filling viscous fluids, which is challenging under the stringent cleanliness requirements for medical devices.
Innovation Solution
A two-piece outer piston rod design allows for preassembly of the viscous fluid-filled first piston rod part with a fluid displacement element, enabling easier assembly and reduced risk of contamination, with the option to use different materials for each part to optimize performance, and filling under vacuum to prevent air bubbles and ensure a tight seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a viscous fluid is filled into the piston rod assembly during assembly, then the delay mechanism functions to prevent premature needle withdrawal, but the manufacturing process becomes extremely delicate and time-consuming due to stringent cleanliness requirements
Solution Approach 1:
The outer piston rod is divided into two separate parts: a first outer piston rod part containing the cavity to be filled with viscous fluid, and a second outer piston rod part. This segmentation allows the cavity to be pre-filled and sealed as a separate unit, avoiding the need to fill the fluid through the entire assembled device and reducing contamination risks during assembly.
Solution Approach 2:
The cavity in the first outer piston rod part is pre-filled with viscous fluid before final assembly with the second outer piston rod part. This preliminary action allows the fluid filling to be performed under controlled conditions with proper sealing, eliminating the need for delicate post-assembly filling operations and ensuring cleanliness requirements are met.
2Ease of manufacture
If the outer piston rod is formed in two parts to simplify assembly, then the manufacturing process becomes easier and more compact, but the device structure becomes more complex
Solution Approach 1:
The first and second outer piston rod parts are connected to form a unified outer piston rod structure that functions as a single component during operation. While manufactured separately for ease of assembly, the two parts merge into one functional unit, minimizing the perceived complexity increase while achieving manufacturing benefits.
Solution Approach 2:
The first outer piston rod part with the cavity is designed to connect with the second outer piston rod part in a nested or interlocking manner. This nesting approach allows the two parts to be manufactured separately but assembled efficiently, reducing overall assembly complexity despite the increased number of components.
3Duration of action of moving object
If viscous fluid is used to delay the release mechanism, then the triggering is delayed as required, but the fluid must be filled under stringent cleanliness requirements increasing production difficulty
Solution Approach 1:
The viscous fluid is pre-filled into the cavity of the first outer piston rod part before final assembly, allowing the filling operation to be performed under controlled conditions with proper sealing in place. This preliminary action ensures the fluid is contained properly without requiring delicate post-assembly filling that would compromise cleanliness.
Solution Approach 2:
The fluid filling operation is extracted from the final assembly process and performed as a separate preliminary step on the first outer piston rod part. This extraction allows the filling to be done in isolation with appropriate containment and sealing, removing it from the stringent cleanliness constraints of the complete device assembly process.
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 simplifies the assembly process, reduces production costs, and allows for a more compact and customizable piston rod unit that effectively delays the triggering mechanism, ensuring accurate and complete delivery of medicinal substances while maintaining cleanliness standards.
Implementation Method 1
The inner piston rod is connected to a rudder-like element that projects into the cavity, which is filled with a viscous fluid. The rotational movement of the inner piston rod is dampened by the rudder-like element, as this encounters resistance due to the fluid in the cavity.
Data Source
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AI summary
The invention relates to a piston rod unit (10) for an administration device (1) for administering a medical substance, wherein the piston rod unit (10) can delay a release of a mechanism of the administration device (1). The piston rod unit (10) comprises an outer piston rod (30) with a hollow space and with a contact face (35) for interacting with a stopper (3a) in order to discharge the substance from a product container (3), an inner piston rod (20), which is mounted in the outer piston rod (30) in such a way that a cavity is formed at the distal end of the outer piston rod (30), said cavity being at least partially filled with a viscous fluid, and a fluid displacement element (14) which is located at least partially in the cavity and interacts with the inner piston rod (20) or is integrally connected to the inner piston rod (20). During a relative movement between fluid displacement element (14) and outer piston rod (30), displacement of the fluid causes a movement resistance, such that the release of the mechanism can be delayed. The outer piston rod (30) is configured in two parts, with a distal, first piston rod part (30a), which comprises the contact face (35) and the cavity, and with a second piston rod part (30b) adjoining the first piston rod part (30a).