Portable Infusion Driving Unit with External Syringe Mounting
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Solution Overview
Problem
Existing portable drug infusion devices are bulky and complex due to the need for protective bellows and thrust bearings, which increase size, cost, and limit syringe capacity, while annular pressure sensors are costly and less frequently used.
Innovation Solution
A driving unit design where the syringe is mounted outside the housing, with a hollow rod sliding between the body and syringe, featuring an internally threaded nut and externally threaded stem, eliminating the need for bellows and thrust bearings, and using a disc-shaped pressure sensor for occlusion detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the threaded rod penetrates inside the syringe to transmit motion to the plunger, then the motion transmission is achieved, but the device requires protective bellows which increase structure complexity and cost
Solution Approach 1:
The patent extracts the threaded rod from the syringe interior by mounting the syringe externally on the housing. The rod now moves between the housing interior and syringe interior without penetrating into the syringe body, eliminating the need for protective bellows and reducing structural complexity while maintaining reliability.
Solution Approach 2:
Instead of having the threaded rod penetrate into the syringe from the housing interior, the patent inverts the arrangement by mounting the syringe externally and having the rod approach the syringe from the housing exterior, thereby avoiding the need for protective barriers.
2Productivity
If the threaded rod penetrates inside the syringe to transmit motion, then motion transmission is achieved, but the pusher size increases and syringe capacity is limited
Solution Approach 1:
The patent removes the bellows and its fastening means from the system by extracting the threaded rod from the syringe interior. This reduces the pusher size and eliminates volume occupation, thereby increasing the effective syringe capacity while maintaining the motion transmission function.
3Device complexity
If the driving system is carried in the front portion of the body, then the structure is compact, but thrust bearings are required to absorb backward thrust which increases complexity and cost
Solution Approach 1:
The patent extracts the thrust bearing from the system by relocating the driving system to the rear portion of the housing. The backward thrust is now naturally absorbed by the rear housing structure itself, eliminating the need for separate thrust bearings and reducing overall device complexity.
4Reliability
If annular pressure sensors are used for occlusion detection, then occlusion detection is achieved, but the device cost increases
Solution Approach 1:
The patent replaces expensive annular pressure sensors with a simpler, more cost-effective disc-shaped pressure sensor that can be integrated into the plunger rod. This maintains reliable occlusion detection functionality while significantly reducing device cost.
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 results in a more compact, cost-effective infusion device with increased syringe capacity and reduced friction, allowing for efficient drug delivery without the need for complex protective mechanisms and costly sensors.
Implementation Method 1
an electric motor suitable for actuate a shaft to rotate
Implementation Method 2
a toothed crown gear driven in rotation by the motor and in engagement with a pinion gear carried by the shaft
Implementation Method 3
an externally threaded stem, integral in rotation with a toothed crown gear... having a rear end portion provided with an internal thread meshing with the external thread of said stem
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A driving unit for a portable drug infusion device (10) comprises an electric motor (24) and a mechanical assembly (21, 27, 28, 40) arranged to convert the rotary motion of the motor (24) into a linear motion and to impart said linear motion to the plunger (17) of a syringe (14) mounted outside a body (11) housing the driving unit. The mechanical assembly (21, 27, 28, 40) includes a toothed crown gear (28) driven by a pinion gear (27) integral with a shaft of the motor (24), and an axially sliding rod (21) carrying, at a front end, a pusher (18) associated with the plunger (17) and moving, during its sliding motion, between the inside of the body (11) and the inside of the syringe (14). The rod (21) has a smooth external surface and an axial cavity (21') housing an externally threaded stem (41) integral in rotation with said toothed crown gear (28) and having a rear end portion provided with an internal thread arranged to mesh with the external thread of said stem (41).