Medical Traction System with Low Back-Travel Cam Mechanism
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Solution Overview
Problem
Existing surgical traction devices are inconvenient in the operating room due to their bulkiness, difficulty in sterilization, slow adjustment, and potential for undesired twisting and limited adjustment range, as well as challenges in assessing the applied traction force.
Innovation Solution
A compact medical traction system featuring a traveler with a handle and cam mechanism that allows direct tensioning of the traction strap along an elongate track, providing rapid and intuitive control with low back-travel and automatic locking, enabling a single operator to accurately apply traction force without the need for additional biasing mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a turnbuckle mechanism is used to adjust traction strap length, then the device is simple and easy to manufacture, but it imparts undesired twisting to the strap, is slow to adjust, has limited adjustment range, and makes it difficult to assess the traction force
Solution Approach 1:
The patent replaces the turnbuckle's screw-threaded mechanical adjustment system with a cam-based mechanical advantage system. The cam mechanism allows for rapid adjustment by rotating the cam, which moves the traveler along the track, providing both speed and intuitive feedback through the mechanical advantage ratio between the cam radius and the traveler displacement.
Solution Approach 2:
The patent changes the adjustment mechanism from linear screw-threaded motion to rotational cam motion. This parameter change enables faster adjustment speeds, eliminates twisting of the strap, and provides a wider adjustment range while maintaining simplicity. The cam's geometric parameters can be optimized to provide the desired mechanical advantage and adjustment characteristics.
2Ease of operation
If a slide and locking knob is used to tension the strap, then intuitive tension control is achieved, but there is undesirable relaxation in the traction force due to strap elasticity between tensioning and locking
Solution Approach 1:
The patent applies preliminary action by having the cam mechanism automatically lock the traveler in position immediately upon release of the tensioning force. The cam's geometry ensures that as the traveler moves along the track during tensioning, the cam surface continuously engages with the track, pre-locking the position before the operator completes the tensioning stroke, thereby eliminating relaxation due to strap elasticity.
Solution Approach 2:
The patent implements feedback through the mechanical advantage system where the force applied to tension the strap is directly transmitted through the traveler and cam mechanism. The operator feels the tension force through the handle, providing real-time feedback on the traction force being applied, while the cam mechanism ensures this force is immediately locked in place.
3Measurement precision
If cables and weights are used for traction, then the traction force is well defined, but the device is bulky, blocks access to the patient, and is difficult to sterilize and adjust
Solution Approach 1:
The patent extracts the essential function of defining traction force from the bulky cable-and-weight system. By using a compact traveler mechanism that moves along a fixed track, the system eliminates the need for large weights and cables while maintaining precise control over the traction force through the mechanical advantage of the cam-traveler interaction.
Solution Approach 2:
The patent creates a universal traction mechanism where the traveler-cam system can be adjusted to provide different traction forces by changing the cam rotation angle, eliminating the need for multiple fixed weights. The same compact mechanism serves both force definition and adjustment functions, reducing device bulk and improving sterilization capability.
4Reliability
If the traveler is locked on the track in fixation state, then the traction force is maintained, but the adjustment range is limited by the track length
Solution Approach 1:
The patent applies dynamics by allowing the traveler to move dynamically along the entire length of the track for adjustment, then lock in place at any position. The cam mechanism can be rotated to any angle, enabling continuous adjustment across the full track length, and then locked at the desired position to maintain traction force. This dynamic-adjustment-then-lock approach provides both wide adjustment range and reliable force maintenance.
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
Enables rapid, intuitive, and precise tensioning of patient limbs with minimal back-travel, improving surgical efficiency and reducing the risk of traction force relaxation, while allowing for easy sterilization and integration into the surgical suite.
Implementation Method 1
The traveler provides a cam mechanism automatically locking the slide when tension is released with low back-travel
Implementation Method 2
an upwardly extending lever and first and second cam surfaces engaging with the elongate track to: (a) allow free sliding of the traveler along the track in an adjustment state with the upwardly extending lever within the first angular range about a horizontal axis
Data Source
AI summary
A medical traction system provides an elongate track having a slide with a handle so that tensioning of the strap can be performed directly on the slide with improved tension sensitivity. The slide provides a cam mechanism with low back-travel automatically locking the slide when tension is released permitting one-handed operation.