Injection Dosing Device Stop Element Prevents Over-Dosing
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Solution Overview
Problem
Existing injection devices lack an effective mechanism to prevent the setting of doses that exceed the amount of medicament available in the cartridge, leading to potential hazardous adverse dosing due to limited product volume.
Innovation Solution
A drive and dosing device with a stop element that engages a thread on the piston rod, preventing dose setting beyond the available medicament volume by using a rotation member and a dose setting mechanism that includes a stop limiter and catch, ensuring the dose is within the cartridge's nominal volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a dose setting mechanism allows free rotation to set any dose value, then the ease of operation is improved, but the reliability deteriorates due to potential over-dosing beyond available medicament volume
Solution Approach 1:
The stop element is pre-positioned on the piston rod at a location corresponding to the available medicament volume. When the dose setting mechanism rotates the piston rod, the stop element engages with a stop limiter before the dose can exceed the available volume, thereby preemptively preventing over-dosing before it can occur.
Solution Approach 2:
The stop element acts as an intermediary mechanical component between the dose setting mechanism and the piston rod. It translates the rotational position of the piston rod into a physical blocking action when the maximum dose is reached, mediating between user input and system limits.
2Reliability
If a stop mechanism is added to prevent over-dosing, then the reliability is improved, but the device complexity increases due to additional components
Solution Approach 1:
The stop element is integrated with the piston rod structure, and the stop limiter is incorporated into the existing dose setting mechanism housing. This merging of functions allows the stop mechanism to be achieved with minimal additional components, combining the dosing and safety functions into a unified system.
Solution Approach 2:
The piston rod serves multiple functions: it transmits the rotational motion from the dose setting mechanism, delivers the medicament through axial movement, and incorporates the stop element that provides the safety limiting function. This multi-functionality reduces the need for separate dedicated stop components.
3Productivity
If the stop element is positioned to allow maximum dose setting, then the productivity is improved, but the manufacturing precision must be very high to ensure accurate positioning
Solution Approach 1:
The stop element is pre-positioned on the piston rod during assembly at a location that corresponds to the available medicament volume. This preliminary positioning ensures that the maximum dose is correctly limited before the device is put into use, allowing the dose setting mechanism to operate through its full range without requiring high precision during operation.
Solution Approach 2:
The stop element automatically engages with the stop limiter when the piston rod rotates to the position corresponding to the maximum dose. This self-acting mechanism eliminates the need for external adjustment or high-precision control systems, allowing the device to self-regulate the maximum dose based on the pre-set mechanical stop position.
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
Prevents over-dosing by ensuring the set dose does not exceed the available medicament, providing reliable and safe administration by blocking further dose increments when the maximum volume is reached, thus preventing medication errors.
Implementation Method 1
the stop element has a thread engaging a further thread of the piston rod
Data Source
AI summary
Drive and dosing devices for injection devices are disclosed. An embodiment may include a threaded piston rod moveable in a dispensing direction for dispensing a product. A rotation member may be operatively connected to a stop limiter and threadably engaged with the piston rod. Rotation of the rotation member may cause the piston rod to move in the dispensing direction. An embodiment may include a dose knob rotatable for changing a dose. The device may further include a stop element threadably engaged with the piston rod and having a catch. The dose knob may be coupled with the stop element such that during increase of a dose, the stop element is screwed toward the distal end of the piston rod and the catch is moved towards the stop limiter. The stop element prevents increasing a dose when the catch abuts the stop limiter.