Automatic Ratcheting Screwdriver Cammed Collar Locking Mechanism
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Solution Overview
Problem
Existing spinal fixation screwdrivers often have locking mechanisms that can unintentionally unlock during use, leading to inefficiencies and potential complications during surgery, particularly in procedures involving pedicle screws.
Innovation Solution
A screwdriver design featuring a spring-biased pawl and cammed collar mechanism that automatically locks and unlocks, preventing accidental loosening, and is compatible with both standard and reduction screws, allowing for efficient operation with robotic assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If button locks or slide locks are used in the screwdriver, then the locking mechanism can be simple in structure, but the reliability is reduced because they can become unlocked during use unintentionally
Solution Approach 1:
The locking mechanism automatically engages and disengages through the rotation of the collar itself, without requiring separate locking actions or additional components. The cam surface on the collar directly actuates the pawl to engage or disengage from the splines based on the direction of collar rotation, making the system self-servicing and eliminating the need for button presses or slide movements.
Solution Approach 2:
The patent replaces traditional button locks or slide locks with a cam-based mechanical system. The cam surface on the collar converts rotational motion into linear motion of the pawl, creating a more reliable locking action that prevents unintentional disengagement while maintaining structural simplicity.
2Reliability
If a secure locking mechanism is implemented to prevent unintentional unlocking, then the reliability is improved, but the device complexity increases due to additional components like spring-biased pawl and cammed collar
Solution Approach 1:
The locking function is merged with the collar rotation operation. The same collar that provides manual control or robotic interface also serves as the actuating mechanism for the pawl through its cam surface. This integration eliminates the need for separate locking components and reduces overall device complexity while maintaining high reliability.
Solution Approach 2:
The spring-biased pawl automatically engages with the splines when the collar is rotated in the locking direction, and automatically disengages when rotated in the unlocking direction. The spring provides continuous biasing force without requiring additional actuators, making the system self-regulating and reducing component count.
3Ease of operation
If manual locking operations are required during screwdriver use, then the ease of operation is reduced requiring time and attention by the operator, but the device complexity can be kept lower
Solution Approach 1:
The locking and unlocking actions occur automatically as by-products of the normal collar rotation during screwdriver operation. When the collar is rotated to advance or retract the screwdriver shaft, the cam surface automatically engages or disengages the pawl, eliminating the need for separate manual locking operations and improving operational efficiency without significant complexity increase.
Solution Approach 2:
The locking mechanism is pre-configured with the spring-biased pawl positioned to engage the splines automatically. The cam surface on the collar is pre-shaped to guide the pawl into engagement during normal operation, so that locking occurs as a preliminary or simultaneous action with the main function, not as a separate step requiring operator attention.
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
The screwdriver ensures secure and efficient screw placement by automatically locking and unlocking, reducing the risk of screw loosening and enhancing surgical efficiency, especially when used with robotic systems.
Implementation Method 1
A spring-biased pawl is disposed within the cavity of the first body and engageable with the spline member of the second body
Implementation Method 2
The spring may be in the form of a c-clip spring
Implementation Method 3
The collar is rotatable relative to the first body and the second body and has a cammed inner surface. When the collar is rotated in a first direction about the first body, the cammed inner surface pushes the spring-biased pawl into engagement with the spline member
Data Source
AI summary
A screwdriver for driving a screw in bone includes a first body configured to engage a tulip of the screw, a first central bore extending through the first body, a second body having a second central bore extending through the second body and an external surface having a spline member positioned at least partially within the cavity, an inner shaft configured to drive a screw into bone and being rotatably coupled with the second body, a spring-biased pawl engageable with the spline member of the second body, a collar rotatable relative to the first body and the second body and having a cammed inner surface, when the collar is rotated in a first direction about the first body, the cammed inner surface pushes the spring-biased pawl into engagement with the spline member to rotatably couple the first body and the second body.