Injection Device Dose Setting Mechanism
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Solution Overview
Problem
Existing injection devices are not user-friendly for patients to easily and intuitively set the desired injection dose, and their operation is not straightforward, requiring complex instructions for proper use.
Innovation Solution
The injection device features a dosing element with a graduated tube and a nut mechanism that allows patients to set the dose by rotating a rotary knob, which is connected to a piston rod through a threaded engagement, preventing rotation during injection to ensure precise dose delivery, and includes a compression spring for easy cartridge replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a threaded nut mechanism is used for dose adjustment, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The dose adjustment mechanism is nested within the injection device housing, with the graduated tube containing the threaded nut mechanism. The rotary knob is integrated into the piston rod assembly, creating a compact nested structure that provides precise dose adjustment without increasing overall device complexity
Solution Approach 2:
The threaded nut acts as an intermediary mechanism between the rotary knob and the piston rod, converting rotational motion into precise linear displacement for dose adjustment. This intermediary element enables accurate dose setting while maintaining a relatively simple overall structure
2Ease of operation
If a rotary knob with threaded engagement is used for dose setting, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The graduated tube with clear markings enables patients to independently set the desired dose without requiring complex instructions or assistance. The self-evident scale and simple rotary operation allow users to perform dose adjustment autonomously, improving ease of operation
Solution Approach 2:
The rotary knob provides a curved, ergonomic interface that is intuitive to operate. The rotational motion follows a natural circular path that is easy to grasp and manipulate, enhancing user-friendliness while maintaining a compact design
3Measurement precision
If the piston rod is prevented from rotating during injection, then measurement precision is improved, but ease of operation is worsened
Solution Approach 1:
The piston rod features an asymmetric cross-section that engages with a corresponding asymmetric recess in the driver, preventing rotation during injection. This asymmetric design ensures precise dose delivery by maintaining consistent orientation of the threaded engagement, while the overall injection operation remains straightforward
Solution Approach 2:
The anti-rotation feature is built into the piston rod design before injection begins. The asymmetric geometry is pre-configured to automatically prevent rotation as soon as the driver engages, ensuring measurement precision is maintained throughout the injection process without requiring additional operational steps
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
The device allows patients to easily set and administer precise injection doses with minimal instructions, providing clear dose indication and ensuring proper operation, enhancing user compliance and reducing complexity in assembly and use.
Implementation Method 1
a compression spring for easy cartridge replacement
Implementation Method 2
A piston rod with an external thread that engages with the thread of a delivery sleeve. An axial forward movement of the piston rod causes an injection through a needle
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An injection device (30) has a housing (42, 52) with a recess for receiving a container (34) having a liquid to be injected (32). Furthermore, the device has a first organ (94) for pressing out the injection liquid (32) from such a container (34), and this first organ (94) has an outer threading (92). A dosing organ (66, 88) has an inner threading (90) which engages with the outer threading (92) of the first organ (94), and this dosing organ (66) can rotate together with the first organ (94) relative to the housing (42, 52) for the purpose of selecting a desired injection dosing. A coupling arrangement (K1) serves to produce a rotationally fixed connection between the first organ (94) and the housing (42, 52) during an injection process, and thereby to block a rotation of the first organ (94) relative to the housing (42, 52) during an injection process, however enabling a rotation of the dosing organ (66, 88) relative to the housing (42, 52). This rotation of the dosing organ (66, 88) produces an axial displacement of a first organ in the proximal direction, i.e., toward the patient, said organ being prohibited from rotating, in order to press injection liquid (32) out of such a container (34).