Medical Device Locking Assembly to Prevent Screw Wind-Back
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Solution Overview
Problem
Existing mandibular advancement devices suffer from screw loosening over time, leading to loss of protrusion and decreased treatment efficiency, with previous solutions either reducing the screw's effective range or requiring tight tolerances and being prone to wear.
Innovation Solution
A locking assembly comprising a screw with a threaded shaft and a head having engagement members, and a cap with corresponding engagement members that lock together to prevent the screw from rotating, providing mechanical interference and tactile feedback without relying on friction or tight tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nut-to-lock screw combination is used to prevent screw loosening, then the screw loosening problem is addressed, but the effective range of the screw is reduced
Solution Approach 1:
The invention extracts the locking function from a separate nut component and integrates it into a cap that fits over the screw head. The cap contains an engagement member that mechanically interferes with the screw head's engagement member, providing locking without requiring a separate nut that would reduce the screw's effective range.
Solution Approach 2:
The cap is designed to fit over the screw head, with the engagement member nested within the cap structure. This nesting arrangement allows the locking mechanism to be compact and not extend the overall length of the screw assembly, preserving the effective range.
2Reliability
If an interference fit at the end of the nut is used to prevent screw loosening, then locking is achieved, but very tight tolerances are required and cost increases
Solution Approach 1:
The locking mechanism is segmented into distinct engagement members: one on the screw head and a corresponding one in the cap. These engagement members engage with each other through mechanical interference (such as a protrusion fitting into a depression), providing a positive lock that does not require tight tolerances across the entire nut-screw interface.
Solution Approach 2:
The engagement members act as intermediaries that transfer and secure the locking force. The mechanical interference between the engagement members provides a reliable locking action that is insensitive to variations in manufacturing tolerances of the surrounding components.
3Reliability
If friction-based resistance is used to prevent screw loosening, then initial locking is provided, but resistance decreases over time due to wear
Solution Approach 1:
The engagement members are designed with complementary shapes (such as a protrusion and corresponding depression) that are pre-configured to engage in a specific orientation. This preliminary geometric configuration ensures that when the cap is installed, the engagement members immediately lock in the correct position, preventing any wind-back motion before friction can even act.
Solution Approach 2:
The invention converts the potential harm of wear by eliminating the reliance on friction. Instead of using friction-based resistance that degrades over time, the mechanical interference between engagement members provides a wear-resistant positive lock that maintains its effectiveness throughout the service life of the device.
Data Source
AI summary
A locking assembly (10) for a medical device (1), the device (1) adapted to adjust the position of an upper teeth engagement member to a lower teeth engagement member, the device (1) having a plate, an elongate recess and a block slidable along said recess to adjust the position of the members relative to each other; the locking assembly (10) including: a screw having an elongate shaft having a thread extending substantially towards one end and a head at the other end, the thread adapted to engage the block, the head having at least one engagement member; and a cap having a corresponding at least one engagement member in use to lock the engagement members together to inhibit said screw from rotating in said block.