Telescopic Piston Rod Assembly for Compact Medicament Delivery
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Solution Overview
Problem
Existing medicament delivery devices for diabetes management are too long to be unobtrusively carried, posing difficulties for users with impaired vision and reduced dexterity, and existing telescopic piston rods are not compact enough for smaller syringe sizes.
Innovation Solution
A medicament delivery device featuring a telescopic piston rod assembly with a plunger, key, and drive mechanism that allows axial movement while preventing rotation, utilizing a gear train and motor for compact design and efficient medicament delivery, including a noise reduction mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a lead screw with threaded piston engagement is used to drive the medicament cartridge, then the axial force is effectively transmitted to expel the medicine, but the total device length becomes at least twice the length of the cartridge, making it too long to fit unobtrusively into a jacket pocket or handbag
Solution Approach 1:
The piston rod is constructed with nested telescopic sections that can be inserted one within another. During injection, the sections extend sequentially to provide the full stroke length, then retract back into a compact form for portable storage, reducing the device length from twice the cartridge length to approximately the cartridge length plus minimal overhang
Solution Approach 2:
The piston rod transitions from a static, fixed-length component to a dynamic, variable-length component that adapts its length during operation. The rod extends to full length during the injection phase to maintain structural integrity and force transmission, then contracts to a compact size during transport, allowing the device to meet both functional and portability requirements
2Length of moving object
If a telescopic piston rod with bushings is used to prevent rotation, then the rod can be made shorter, but the bushing of largest diameter must fit within the syringe diameter, limiting the design to syringes of considerable size only
Solution Approach 1:
The anti-rotation mechanism is divided into multiple smaller engagement features distributed along the telescopic rod rather than requiring a single large bushing. The rod includes external screw threads that engage with internally threaded sections in the syringe wall, creating multiple small-scale mechanical interlocks that collectively prevent rotation without requiring any single component to exceed the syringe diameter
Solution Approach 2:
The traditional bushing-based anti-rotation mechanism is replaced with a threaded engagement system. Instead of using a large-diameter bushing that must fit within the syringe, the design uses externally threaded sections on the rod that screw into internally threaded passages in the syringe wall, substituting a compact threaded connection for a bulky bushing and enabling compatibility with smaller syringes
3Ease of operation
If the device is made compact for portability, then it becomes easier to carry, but the drive mechanism and telescopic assembly may become too complex to manufacture and assemble
Solution Approach 1:
Multiple functions are combined into integrated components to reduce the total number of parts. The piston rod simultaneously provides structural support, transmits axial force, enables telescopic length adjustment, and incorporates anti-rotation threading—all in a single integrated component rather than separate elements, simplifying assembly while achieving compact dimensions
Solution Approach 2:
The telescopic piston rod is designed as a multi-functional component that performs multiple roles: it serves as the structural backbone of the device, transmits the injection force from the drive mechanism, provides the telescopic extension and retraction capability for length adjustment, and includes integrated threading for anti-rotation engagement with the syringe. This multi-functionality reduces the number of separate components needed, thereby simplifying the overall assembly process despite the compact design
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 compact design allows for easier handling and use by users with impaired vision and reduced dexterity, enabling efficient medicament delivery with a constant force application, suitable for both single-dose and multi-dose devices, including auto-injectors with replaceable cartridges.
Implementation Method 1
a battery driven motor for driving the transfer drive via a gear train
Implementation Method 2
driving the transfer drive via a gear train
Implementation Method 3
The plunger is provided with an external screw thread that engages with an internal screw thread of the input drive so that rotation of the input drive telescopically moves the plunger into or out of the input drive
Data Source
AI summary
A medicament delivery device comprises a housing, a telescopic piston rod assembly for driving a bung of a medicament container, and a drive mechanism for the telescopic piston rod assembly. The telescopic piston rod assembly comprises a plunger for driving a bung, a key for allowing predominantly axial movement between the plunger and the housing and an input drive telescopically coupled to the plunger and supported for rotational and axial movement relative the housing. The drive mechanism additionally comprises a transfer drive that operates to rotate the input drive. As the input drive rotates, it moves axially relative to the housing, expanding telescopically relative to the plunger.