Bidirectional Toothed Rack Actuation in Surgical Staplers
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Solution Overview
Problem
Existing surgical handle assemblies for surgical staplers lack efficient mechanisms for advancing and retracting the toothed rack, which is crucial for effectively clamping and unclamping the reloadable cartridge assembly.
Innovation Solution
The surgical handle assembly incorporates a toothed rack that is advanced distally by a driving pawl in response to the movable handle member being actuated proximally, and is retracted proximally by a latch when the handle member is actuated distally, allowing for precise control of the cartridge assembly's clamped and unclamped positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a driving pawl is used to advance the toothed rack, then the toothed rack can be advanced distally to clamp the cartridge assembly, but the mechanism lacks an efficient retraction mechanism
Solution Approach 1:
The patent combines the advancement and retraction functions into a single integrated mechanism. The driving pawl serves dual purposes: it advances the toothed rack during clamping and, when disengaged, allows spring-driven retraction during unclamping. This merging eliminates the need for separate actuation systems for both directions, reducing overall device complexity while maintaining ease of operation.
Solution Approach 2:
The mechanism transitions from a static single-direction drive to a dynamic bidirectional system. The driving pawl can engage for advancement and disengage for retraction, allowing the system to adapt its behavior based on operational needs. This dynamic capability enables efficient bidirectional movement without requiring complex separate mechanisms for each direction.
2Force
If the movable handle member is actuated proximally to advance the toothed rack, then clamping force is applied, but precise control of retraction is difficult
Solution Approach 1:
The toothed rack and driving pawl engagement provides mechanical feedback that ensures precise control. The teeth on the rack engage with the pawl in discrete increments, providing controlled positioning during both advancement and retraction. This toothed engagement mechanism prevents slippage and ensures accurate, repeatable positioning of the cartridge assembly in both clamped and unclamped states.
Solution Approach 2:
The spring acts as an intermediary element during retraction. When the driving pawl disengages, the spring provides controlled force to return the toothed rack to its initial position. This intermediary spring mechanism ensures smooth, controlled retraction without requiring direct manual manipulation, achieving precise control while maintaining ease of operation.
3Ease of operation
If a latch is used to retract the toothed rack, then the cartridge assembly can be unclamped, but the mechanism complexity increases
Solution Approach 1:
The driving pawl is designed with multi-functionality, serving both as an advancement mechanism when engaged and as a disengagement element that enables retraction when disengaged. The latch mechanism similarly serves dual purposes: it can lock the toothed rack in place during clamping and release to enable spring-driven retraction during unclamping. This multi-functionality reduces the need for separate dedicated mechanisms, thereby reducing overall device complexity.
Solution Approach 2:
The spring-driven retraction mechanism is self-service in nature. Once the driving pawl is disengaged or the latch is released, the spring automatically provides the force needed to retract the toothed rack without requiring additional actuation or complex control systems. This self-service capability simplifies the overall mechanism by eliminating the need for powered retraction systems.
4Reliability
If the toothed rack is advanced distally to clamp the cartridge assembly, then secure clamping is achieved, but the retraction speed is reduced
Solution Approach 1:
The mechanism employs periodic engagement and disengagement of the driving pawl with the toothed rack. During clamping, the pawl is engaged to provide secure, controlled advancement. During retraction, the pawl is disengaged to allow rapid spring-driven movement. This periodic switching between engaged and disengaged states enables the system to optimize for both secure clamping and fast retraction, achieving high speed during the retraction phase without compromising clamping security.
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
The present disclosure includes apparatuses for a surgical handle assembly. An example apparatus includes a toothed rack, a movable handle member, a driving pawl configured to engage the toothed rack and advance the toothed rack in a linear distal direction in response to a movable handle member advancing in a proximal direction and a latch configured to engage the toothed rack and advance the toothed rack in a linear proximal direction in response to the movable handle member advancing in a distal direction.