Infusion Pump Cassette Latch Over-Travel Locking Mechanism
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Solution Overview
Problem
Infusion pumps often experience unstable coupling with tube cassettes, leading to potential misalignment and inaccuracy in fluid delivery due to meta-stable connections and external forces affecting the infusion tubing, resulting in bolus delivery or volume inaccuracy.
Innovation Solution
A locking system comprising a latch and mechanical stop within the infusion pump that ensures the tube cassette is securely locked in a preset position, preventing meta-stable connections and external forces from affecting the delivery, by allowing 'over-travel' to ensure full engagement and subsequent locking of the cassette.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tube cassette is allowed to insert freely into the pump, then the insertion process is simple and fast, but the connection becomes meta-stable and the cassette may pop out or become misaligned
Solution Approach 1:
The latch is pre-configured in a retracted position that allows free insertion of the tube cassette. Once insertion is complete, the latch automatically transitions to an engaged position to lock the cassette in place, providing preliminary preparation for both insertion ease and subsequent stability
Solution Approach 2:
The latch mechanism is designed to automatically engage and lock the tube cassette in the correct position without requiring manual intervention. The system self-regulates the transition from insertion mode to locked mode, ensuring reliability while maintaining ease of operation
2Reliability
If the latch engages the locking surface early during insertion, then the connection stability is improved, but the latch may get stuck in a meta-stable position and fail to achieve full engagement
Solution Approach 1:
The mechanical stop is pre-positioned to define an over-travel position that ensures the latch will engage the locking surface at the correct point in the insertion sequence, preventing premature engagement and meta-stable states
Solution Approach 2:
The mechanical stop acts as an intermediary element that mediates between the latch and the tube cassette. It controls the timing and position of latch engagement by allowing the cassette to over-travel past the preset position, ensuring the latch only engages when properly aligned
3Manufacturing precision
If the tube cassette is locked rigidly in position, then the fluid delivery accuracy is improved, but the device complexity increases due to the locking mechanism
Solution Approach 1:
The latch mechanism automatically performs the locking function without requiring additional actuators or complex control systems. The spring-loaded latch self-activates upon completion of insertion, providing rigid positioning through a simple mechanical design that minimizes overall device complexity
Solution Approach 2:
The patent replaces complex electronic or motorized positioning systems with a purely mechanical latch and spring mechanism. This mechanical substitution achieves precise positioning and rigid locking while reducing device complexity by eliminating motors, sensors, and electronic controls
Data Source
AI summary
A tube cassette (22) for receiving infusion tubing is shaped to define a locking surface (26). A pump (20) includes a latch (28) which engages with the locking surface and locks the cassette in a preset position with respect to the pump. A mechanical stop (38) in the pump stops motion of the cassette in a first direction, such that the cassette has moved past the preset position. Until motion of the cassette is stopped by the mechanical stop, the latch allows motion of the cassette past the preset position in the first direction. The latch automatically moves from an open position to a cassette-withdrawal-inhibiting position upon engagement of the latch with the locking surface, and subsequently locks the cassette in the preset position by pushing the cassette in a second direction, from past the preset position to the preset position. Other applications are also described.