Syringe Plunger Rod Locking Device for Single-Use Prevention
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Solution Overview
Problem
Conventional syringes lack an effective and cost-efficient mechanism to prevent re-use after use, which is crucial for preventing disease transmission and misuse.
Innovation Solution
A locking device that positively locks the plunger rod at or near the foremost axial position within the syringe barrel, using a disc-shaped proximal end and a chamber with side-walls or shielding webs to prevent withdrawal and provide a tamper-evident indication of use, allowing intuitive recognition of the syringe's status.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking device is added to prevent re-use of syringes, then reliability of single-use prevention is improved, but device complexity increases
Solution Approach 1:
The locking device integrates multiple functions into a single component: the circumferential side-wall forms both the structural boundary of the locking device and the chamber for receiving the plunger rod proximal end, while also providing mounting attachment means. This merging reduces the number of separate parts and simplifies the overall device structure while maintaining reliable re-use prevention functionality.
Solution Approach 2:
The circumferential side-wall serves multiple purposes simultaneously: it defines the chamber volume, provides structural support, offers mounting attachment means for securing the locking device to the syringe barrel, and creates the receiving space for the plunger rod proximal end. This multi-functionality reduces component count and device complexity while ensuring reliable single-use prevention.
2Reliability
If a locking device with chamber and side-walls is used to prevent plunger rod withdrawal, then reliability of re-use prevention is improved, but ease of operation deteriorates
Solution Approach 1:
The locking device is pre-configured with the chamber and side-walls in a ready state before syringe use. The mounting attachment means are prepared in advance to secure the locking device to the syringe barrel, and the chamber is pre-formed to receive the plunger rod proximal end. This preliminary preparation ensures that the locking mechanism is already in place to prevent re-use, while the simple geometric design maintains ease of operation.
3Ease of manufacture
If a simple geometric configuration is used for the locking device, then ease of manufacture is improved, but reliability of tamper-evident indication may deteriorate
Solution Approach 1:
The locking device employs simple geometric forms (cylindrical chamber, circumferential side-wall) for ease of manufacture, while local features such as the precisely dimensioned chamber volume and the interaction between the side-wall and plunger rod proximal end create reliable tamper-evident indication. The local geometric relationships ensure that any attempt to manipulate the plunger rod after use is visually detectable, maintaining reliability without complicating manufacturing.
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The invention relates to a locking device for locking a plunger rod 5 of a syringe after use and preventing re-use of the syringe. The device comprises a mounting portion 40 configured for mounting the locking device 2 on the flange 13 and a plunger rod locking portion 30 for the plunger rod 5 after use of the syringe, wherein a communication channel 29 is formed in the locking device 2 for enabling insertion of the plunger rod 5 into the barrel 10. According to the invention, a chamber 37 of a width larger than a width of the communication channel 29 is formed inside the plunger rod locking portion 30 for receiving the disc-shaped proximal end 50 of the plunger rod 5 after use of the syringe. The plunger rod locking portion 30 comprises at least one positive locking device 34 configured to positively lock the axial position of the plunger rod 5 by positive-fit engagement with the disc-shaped proximal end 50 of the plunger rod 5 and preferably configured to retain the disc-shaped proximal end 50 of the plunger rod 5 inside the chamber 37, for locking the plunger rod 5 at or near a foremost axial position of a distal end 51, 53 of the plunger rod 5 in the barrel 10 after use of the syringe. The locking device provides the functionality of a tamper-evident plunger rod locking device once a dose of medication has been injected by pushing the plunger rod forward, for preventing inadvertent re-use of the syringe.