Viscous Liquid Damping for Medicament Delivery Speed Control

The patent introduces a hydraulic damping mechanism where a viscous liquid is contained in a chamber with narrow passages. The plunger rod interacts with this liquid, creating hydraulic resistance that controls the movement speed. The compression spring drives the plunger rod, but the viscous liquid in the narrow passages dampens the motion, converting the uncontrolled mechanical energy into controlled flow through the liquid, thus achieving speed control while maintaining automatic operation.

The patent changes the flow resistance parameter by using a viscous liquid with specific viscosity and narrow passages of controlled cross-sectional area. This creates a damping effect that limits the speed of medicament delivery. The narrow passages create a pressure drop that prevents too-rapid injection, thereby avoiding foaming and patient discomfort while still delivering the medicament efficiently. The parameters of the liquid (viscosity) and the passages (cross-sectional area, length) can be adjusted to optimize the balance between injection speed and comfort.

The patent employs a self-regulating hydraulic damping system where the viscous liquid automatically provides speed control based on the flow rate. The narrow passages create inherent flow resistance that limits the plunger rod speed without requiring external control mechanisms. The system self-adjusts to the driving force from the compression spring, providing passive speed control. This approach avoids adding complex active control systems, motors, or electronic controllers, thus maintaining device simplicity while achieving speed control.

The patent optimizes the balance between damping effect and pressure loss by carefully selecting the viscosity of the viscous liquid and the dimensional parameters of the narrow passages (cross-sectional area, length, shape). The passages are designed with sufficient cross-sectional area to maintain acceptable pressure loss while being narrow enough to provide the necessary damping effect. The length of the passages can be adjusted to fine-tune the pressure drop. By optimizing these parameters, the system achieves effective speed control without excessive pressure loss that would compromise medicament delivery efficiency.